Resilience of the PNT Systems - CORE

Catarina de Sousa Matos Aresta

Resilience of the PNT Systems

A Portuguese Case Study

Dissertação para obtenção do grau de Mestre em Ciências Militares

Navais, na especialidade de Marinha

Alfeite 2017

Anexo 2

Catarina de Sousa Matos Aresta

Resilience of the PNT Systems

A Portuguese Case Study

Dissertação para obtenção do grau de Mestre em Ciências Militares Navais, na

especialidade de Marinha

Orientação de: CFR Plácido da Conceição

O Aluno Mestrando O Orientador

[nome] [nome]

Alfeite

2017

IV

Resilience of the PNT Systems: A Portuguese Case Study

V

“Resilience is very different than being numb. Resilience means you experience, you

feel, you fail, you hurt. You fall. But, you keep going.”

Yasmin Mogahed

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VII

To my family for their support but, in a more special way, to

my sister Rita for being an example of eloquence, brilliance

and persistency.

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Acknowledgements

Firstly, I would like to thank my Thesis Supervisor, Commander Plácido da

Conceição, for guiding me throughout the whole research process, always keeping me

motivated and interested in finding out more about this theme.

Secondly, I would like to thank Lieutenant Commander Figaldo Neves, for offering

me help throughout the technical and experimental aspects of my study.

Thirdly, but just as important, I would like to thank all the Organisations and

participants that helped me throughout this project: Gabinete Nacional de Segurança,

Direção Geral do Território, Autoridade Marítima Nacional, Centro de Informação

Geoespacial do Exército, Portuguese Air Force, Svitzer, Faculdade de Ciências da

Universidade de Lisboa, GMV, Vessel Traffic Service, Comando Naval for providing a naval

unit for my experiment, Centro Integrado de Treino e Avaliação Naval, Centro de

Comunicações Dados e Cifra da Marinha, Esquadrilha de Submarinos, Esquadrilha de

Helicópteros, NRP D. Francisco de Almeida, NRP Bartolomeu Dias, NRP António Enes, NRP

Arpão, Direção de Navios and Instituto Hidrográfico.

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Abstract

There is a high national dependency on Position, Navigation and Timing (PNT)

Systems for several individuals, services and organisations that depend on this

information on a daily basis. Those who rely on precise, accurate and continuous

information need to have resilient systems in order to be highly efficient and reliable. A

resilient structure and constantly available systems makes it easier to predict a threat or

rapidly recover in a hazardous environment.

One of these organisations is the Portuguese Navy, whose main purposes are to

combat and maintain maritime safety. In combat, resilient PNT systems are needed for

providing robustness in case of any threat or even a simple occasional system failure. In

order to guarantee maritime safety, for example in Search and Rescue Missions, the need

of PNT information is constant and indispensable for positioning control.

The large diversity of PNT-dependent equipment, developed over the last two

decades, is a valid showcase for the high GPS dependency that is seen nowadays – which

is vulnerable to various factors like interference, jamming, spoofing and ionospheric

conditions. The recent interest over integrated PNT system resolutions is related to the

search for redundancy, accuracy, precision, availability, low cost, coverage, reliability and

continuity.

This study aimed to build a current PNT Portuguese picture based on Stakeholder

Analysis and Interviews; assess the vulnerability of those who depend mainly on GPS for

PNT information and, find out what the next steps should be in order to create a National

PNT Strategy.

Key-words: Resilience, PNT, GNSS, Stakeholders, Vulnerability.

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Resumo

Existe uma elevada dependência nacional em sistemas de Posição, Navegação e

Tempo (PNT) por parte de diversos indivíduos, serviços e organizações que dependem

desta informação no seu dia-a-dia.

Todos os que dependem de informação precisa, exata e contínua, necessitam de

ter sistemas resilientes para que sejam altamente eficientes e fiáveis. Uma estrutura

resiliente e sistemas continuamente disponíveis facilitam a previsão de possíveis ameaças

ou a expedita recuperação da funcionalidade, em ambientes hostis.

Uma destas organizações é a Marinha Portuguesa cujas funções principais são o

combate, a salvaguarda da vida humana no mar e a segurança marítima e da navegação.

Para o combate, são necessários sistemas PNT, resilientes, que ofereçam robustez em

caso de uma simples ameaça ou falha temporária dos sistemas. Por forma a ser possível

cumprir a missão, a necessidade de ter informação PNT, fidedigna e atualizada, é

constante e indispensável para o controlo preciso e exato da posição. Uma unidade naval,

por forma a permanecer continuamente no mar, manter a sua prontidão, treinar a sua

guarnição ou ser empenhada num cenário de guerra, necessita de saber, com confiança e

sem erros, a sua posição e referência de tempo.

A grande diversidade de sistemas dependentes de informação PNT, desenvolveu-

se em larga escala nas últimas duas décadas e sustenta cada vez mais a alta dependência

do GPS, que é vulnerável a diversas fontes de erro, tais como interferência,

empastelamento, mistificação e condições ionosféricas. Atualmente, o elevado interesse

na criação de sistemas PNT integrados está associado à procura da redundância, exatidão,

precisão, disponibilidade, baixo custo, cobertura, fiabilidade e continuidade.

Este estudo teve como objetivos construir o panorama atual, em Portugal, ao nível

dos Sistemas PNT, baseando-se numa análise de Stakeholders e entrevistas; avaliar a

vulnerabilidade de organizações e serviços que dependam exclusivamente do GPS como

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fonte de informação PNT; e propor um possível caminho para que seja possível criar uma

Estratégia PNT Nacional.

Palavras-chave: Resiliência; PNT; GNSS; Stakeholders; Vulnerabilidade.


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Contents

Acknowledgements ............................................................................................................... IX

Abstract ................................................................................................................................. XI

Resumo ................................................................................................................................ XIII

Contents ............................................................................................................................... XV

List of figures ...................................................................................................................... XVII

List of Tables ........................................................................................................................ XXI

List of Abbreviations and Acronyms .................................................................................. XXIII

Introduction ............................................................................................................................ 1

Chapter 1 – What are resilient PNT Systems? ........................................................................ 7

1.1 What is Resilience? .......................................................................................................... 7

1.2 The path to PNT ............................................................................................................. 11

1.2.1 Looking through GNSS ............................................................................................ 11

1.2.2 What are PNT Systems? .......................................................................................... 19

1.2.3 Alternative PNT information sources ...................................................................... 20

1.2.4 How to seek resilience in a PNT System? ............................................................... 33

Chapter 2 – GNSS Vulnerabilities ......................................................................................... 39

2.1 Vulnerabilities ................................................................................................................ 39

2.1.1 Interference ............................................................................................................ 41

2.1.2 Ionospheric effects .................................................................................................. 42

2.1.3 Jamming and jamming trials ................................................................................... 43

2.1.4 Spoofing and spoofing trials ................................................................................... 46

Chapter 3 – Methodology ..................................................................................................... 51

3.1 Resilience analysis ......................................................................................................... 51

3.2 Stakeholder analysis ...................................................................................................... 54

3.3 Resilience in operations – Jamming Trial ...................................................................... 57

Chapter 4 –Results ................................................................................................................ 61

4.1 Portuguese PNT Stakeholders point of view and needs ............................................... 61

4.1.1 Online Questionnaire .............................................................................................. 61

4.1.2 Open interview ........................................................................................................ 67

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4.2 Jamming Trial ................................................................................................................. 68

4.2.1 First Trial .................................................................................................................. 70

4.2.2 Second Trial ............................................................................................................. 71

4.2.3 Third Trial ................................................................................................................ 72

4.2.4 Spectrum Analyzer .................................................................................................. 74

Chapter 5 – Analysis ............................................................................................................. 77

5.1 Portuguese PNT stakeholders ....................................................................................... 77

5.2 Portuguese PNT actual picture ...................................................................................... 83

5.3 Jamming Trial ................................................................................................................. 85

Chapter 6 – A path for a resilient PNT System in Portugal ................................................... 93

Conclusion ............................................................................................................................ 97

Bibliography .......................................................................................................................... 99

APPENDIX A ........................................................................................................................ 107

APPENDIX B ......................................................................................................................... 109

APPENDIX C ......................................................................................................................... 113

APPENDIX D ........................................................................................................................ 121

APPENDIX E ......................................................................................................................... 123

APPENDIX F ......................................................................................................................... 129

APPENDIX G ........................................................................................................................ 135

APPENDIX H ........................................................................................................................ 141

APPENDIX I .......................................................................................................................... 143


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List of figures

Figure 1 - Ships’ equipment using GPS ................................................................................. 12

Figure 2 - Generations of Loran's performance ................................................................... 23

Figure 3 - Korean jamming incidents .................................................................................... 24

Figure 4 - Micro-electro-mechanical System Coriolis Vibratory Gyroscope ........................ 28

Figure 5 - Multisensor navigation for a car navigation system ............................................ 32

Figure 6 - STAMP fundamental concepts ............................................................................. 53

Figure 7 - Trial event sheet ................................................................................................... 59

Figure 8 - General questionnaire results .............................................................................. 66

Figure 9 - Commons topics – Open Interviews (MAXQDA12) .............................................. 67

Figure 10 - Topics 'Solutions' and ' Alternatives' .................................................................. 68

Figure 11 - Latitude Variation (1st Trial) ............................................................................... 70

Figure 12 - Longitude Variation (1st Trial) ............................................................................ 70

Figure 13 - Speed Variation (1st Trial) .................................................................................. 71

Figure 14 - Latitude Variation (2nd Trial) ............................................................................. 71

Figure 15 - Longitude Variation (2nd Trial) .......................................................................... 72

Figure 16 - Speed Variation (2nd Trial) ................................................................................. 72

Figure 17 - Latitude Variation (3rd Trial) .............................................................................. 73

Figure 18 - Longitude Variation (3rd Trial) ........................................................................... 73

Figure 19 - Speed Variation (3rd Trial) ................................................................................. 73

Figure 20 - Spectrum Analyzer (J242-G model) .................................................................... 75

Figure 21 - Spectrum Analyzer (J220-B model) .................................................................... 76

Figure 22 - Questionnaire results ......................................................................................... 77

Figure 23 - Portuguese Actual PNT Picture .......................................................................... 84

Figure 24 - R&S FSH3 Spectrum Analyzer ............................................................................. 86

Figure 25 - Vulnerability assessment .................................................................................... 88

Figure 26 - Stakeholder's request for participation ........................................................... 107

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Figure 27 - Questionnaire (page 1) ..................................................................................... 109




Figure 31 - Open interview analysis (Users - Time) ............................................................ 113

Figure 32 - Open interview analysis (Academia) ................................................................ 114

Figure 33 - Open interview analysis (Investigation) ........................................................... 115

Figure 34 - Open interview analysis (Users - Navigation) .................................................. 116

Figure 35 - Open interview analysis (Users - Positioning) .................................................. 117

Figure 36 - Open interview analysis (Control & Vigilance Authorities) .............................. 118

Figure 37 - Open interview analysis (GNSS-depend services supplier) .............................. 119

Figure 38 - Open interview analysis (GNSS services supplier) ........................................... 120

Figure 39 - Personal interview ............................................................................................ 121

Figure 40 - Common topics (1) ........................................................................................... 123








Figure 48 - Personal interview results (1) ........................................................................... 129








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Figure 56 - R&S FSH3 Antenna ........................................................................................... 135

Figure 57 - Trial equipment (R&S FSH3) ............................................................................. 135

Figure 58 - Putty program .................................................................................................. 136

Figure 59 - R&S FSH3 .......................................................................................................... 136

Figure 60 - AIS "no sensor position" ................................................................................... 137

Figure 61 - AIS "UTC sync invalid" ...................................................................................... 137

Figure 62 - ECDIS (AIS alarm) .............................................................................................. 138

Figure 63 - ECDIS (No fix) .................................................................................................... 138

Figure 64 - Radar KH1007 (loss of position) ....................................................................... 139

Figure 65 - GPS Furuno - no fix ........................................................................................... 139

Figure 66 - VHF sailor (no satellite sync) ............................................................................ 140

Figure 67 - VHF sailor (distress failure) ............................................................................... 140

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List of Tables

Table 1 – Impact of "A day in the UK without GNSS" ........................................................... 41

Table 2 - Table 2 - NLV "Pole Star" Jamming Trial Results ................................................... 45

Table 3 – Primary, Secondary and Key Stakeholders ........................................................... 56

Table 4 - Trial Schedule ......................................................................................................... 58

Table 5 - Equipment failure during Jamming Trials .............................................................. 69

Table 6 - Jammers impact (1,10,30,50m) ............................................................................. 88

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XXIII

List of Abbreviations and Acronyms

AAPS – Automatic Identification System Autonomous Positioning System

AIS – Automatic Identification System

APNT – Alternative Position, Navigation and Timing

ASF - Additional Secondary Factor

AtoN – Aids-to-Navigation

BDS – BeiDou Navigation Satellite System

C/A-code – Coarse/Acquisition code

CDMA – Code Division Multiple Access

CRPA - Controlled Radiation Pattern Antennas

CSAC – Chip scale atomic clock

C-SCAN - Chip-Scale Combinatorial Atomic Navigator

DARPA - Defense Advanced Research Projects Agency

DASS – Distress-alerting Satellite System

DCS – Data Coding Scheme

DGPS – Differential Global Positioning System

DME – Distance Measuring Equipment

DSC - Digital Selective Calling

EDTR – e-LORAN Differential Time Receiver

EGNOS – European Geostationary Navigation Overlay System

e-LORAN – enhanced-long range navigation

ESA – European Space Agency

EU – European Union

EUROCONTROL – European Air Traffic Control

FDMA – Frequency Division Multiple Access

GAGAN – GPS-Aided GEO Navigation System

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GAARDIAN - GNSS Availability Accuracy Reliability and Integrity Assessment for timing and

Navigation

GAUL - Galileo Assist Using e-LORAN

GBT – Ground Based Transceiver

GEO - Geostationary

GLA - The General Lighthouse Authorities of the United Kingdom and Ireland

GLONASS – Globalnaya Navigatsionnaya Sputnikovaya Sistema (Global Navigation Satellite

System)

GMDSS – Global Maritime Distress Safety System

GNSS – Global Navigation Satellite System

GPS – Global Positioning System

GPSS – Global Positioning system-of-systems

GSM - Global System for Mobile Communications

HRO - High-Reliability Organisation

ID – Investigation and Development

IMO – International Maritime Organization

IMU – Inertial Measurement Unit

INS – Inertial Navigation System

IRSS – Indian Regional Satellite System

ISRO – Indian Space Research Organization

ITU – International Telecommunications Union

LDC – Loran Data Channel

LF – Low-Frequency

MCC – Mission Control Centres

MEO – Medium Earth Orbit

MF – Medium-frequency

MSAS – Multi-functional Satellite Augmentation System

NATO – North Atlantic Treaty Organization


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NDGPS – National Differential Positioning System

NLES – Navigation Land Earth Stations

NMEA - National Marine Electronics Association

NTP – Network Time Protocol

P-code – Precision code

PDU - Power Distribution Unit

PHM - Passive Hydrogen Maser

PNT – Position, Navigation and Timing

PPS - Precise Positioning Service

PRN – Pseudo Random Noise

QZSS – Quasi-Zenith Satellite System

RAFS - Rubidium Atomic Frequency Standard

RAIM - Receiver Autonomous Integrity Monitoring

RIMS – Ranging and Integrity Monitoring Stations

RF – Radio Frequency

RNSS – Regional Navigation Satellite System

RTK – Real Time Kinematics

SAASM - Selective Availability Anti-Spoofing Module

SBAS – Space-based Augmentation System

SDCM – System for Differential Corrections and Monitoring

SENTINEL - GNSS Services Needing Trust in Navigation, Electronics, Location & Timing

SIS – Signal-in-space

SNR - Signal-to-Noise Ratio

SOP – Standard Operational Procedures

STAMP - Systems-Theoretic Accident Modelling and Processes

SPS - Standard Positioning Service

TAI - International Atomic Time

TOA – Time of Arrival

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UK – United Kingdom

UPS - Uninterruptible Power Supply

U.S. – United States

USA – United States of America

UTC – Coordinated Universal Time

VHF – Very High Frequency

VTS - Vessel Traffic Service

WAAS – Wide Area Augmentation System

WAGE – Wide Area GPS Enhancement

WARTK – Wide Area Real Time Kinematics


1

Introduction

What would we do if suddenly our positioning and timing satellites were instantly

turned off? Most things we do on a daily basis use Global Navigation Satellite Systems

(GNSS) as a position, navigation or time reference: ships, aircrafts, cars, electricity

distribution companies, national defence departments and even citizens. “Over 130,000

manufacturing jobs and over 3 million people are involved in some aspect of the

downstream GNSS markets for their livelihoods. The commercial value of the direct and

indirect markets are difficult to precisely define, but is in the range of US$100 billion per

year in the United States alone. Worldwide it exceeds $175 billion.”1

The Global Positioning System (GPS), one of the mostly used PNT systems of

nowadays, is almost the only available option for civil and military marine navigation in

most countries. However, this system is very vulnerable to ionospheric2 or accidental

interference3, jamming or spoofing4. This leaves warships only with few or no alternatives

to assure continuous PNT information. Without this information or if it is not precise, a

warship will not be able to know its position and time reference in a war scenario or rescue

mission, in an swift manner.

Over the last decade, large developments have been made in the jamming

equipment market, which made buying these cheap gadgets online easier. This means

that one could easily compromise the maritime safety5 and, consequently, the Safety of

1 Scott Madry, Global Navigation Satellite Systems and their Applications, New York, Springer Science +

Business Media LCC, 2015, p 2.

2 Paul Kintner, Todd Humphreys, Joanna Hinks, “GNSS and Ionospheric Scintillation”, Inside GNSS, July/August

Issue, 2009, http://www.insidegnss.com/node/1579, (accessed April 2017).

3 Andrew Dempster, Boaters beware GPS vulnerable to interference and jamming, 2016,

http://www.marinebusinessworld.com/n/Boaters-beware-GPS-vulnerable-to-interference-and-jamming/81275?source=google.pt, (accessed April 2017).

4 Joe Uchill, Why GPS is more vulnerable than ever, http://projects.csmonitor.com/gps, (accessed April 2017).

5 Alan Grant, et al., Understanding GNSS availability and how it impacts maritime safety, San Diego, The

General Authorities of the United Kingdom and Ireland, 2011.

2

Life at Sea by locally denying the use of GPS signals. Under these circumstances, the need

for redundancy and creating new PNT alternatives was intensified. The International

Maritime Organisation’s (IMO) strategy for the e-Navigation adoption6 states that before

developing the Electronic Navigation area, a new robust, redundant positioning system

must be adopted, only initially due to its vulnerabilities – using GNSS. Organisations that

depend on continuous and reliable PNT information need to be equipped with resilient

and robust systems.

The Portuguese Navy, on which this study mostly focuses on, needs to be provided

with accurate PNT information in order to operate far from harbours and coastlines, it is

a High Reliability Organisation (HRO)7 and its missions include military defence in normal

or hazardous conditions, Search and Rescue operations and provision of maritime

navigation safety services.

With the intent of contributing to a current perspective of the Portuguese PNT

dependency and, more specifically, the Portuguese Navy, this study is based on two

convergent lines of investigation. The first part of the investigation consisted in collecting

data on the current Portuguese PNT picture by interviewing, through a questionnaire and

personal interview, the PNT stakeholders. The second part consisted of submitting a

Portuguese Navy naval unit to a GPS-denied environment to make an assessment on its

dependency and decision-making upon an uncommon and unexpected scenario.

Objectives

The central question of this project is: “Why should PNT systems be resilient?”

Secondary questions are then derived from the main question:

● How can a PNT system be resilient?

● What are the Portuguese PNT stakeholders looking for in a PNT system?

● What is the current perspective of PNT systems in Portugal?

6 Sub-Committee on the Safety of Navigation, Development of an E-Navigation Strategy Implementation Plan,

United Kingdom, International Maritime Organisation, 2011, pp 18-25.

7 Daved Stralen, High Reliability Organisations, High Reliability Organizing, http://high-reliability.org/High-

Reliability-Organisations, (accessed April 2017).


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● How are the Portuguese Warships vulnerable to (un)intentional GPS

information denial?

This research starts with a theoretical approach to this theme, including the

definition of resilience and PNT systems. This is followed by clarifications on the

requirements for a resilient PNT System.

The merging of these theoretical concepts with the study about the PNT systems

that are currently available in Portugal and more specifically aboard Portuguese Warships,

it was possible to build a perspective of the Portuguese PNT current picture; to know what

the stakeholders look for in PNT system; to investigate if there is national resilience

awareness and at last but not least, to investigate how Portuguese Warships are

vulnerable to intentional or unintentional GPS denial.

Methodology

This study began with a bibliographic research of articles, publications and books

related to the concepts of resilience; Position, Navigation and Timing Systems and in

which way are they considered resilient.

Then, an initial stakeholder analysis was made to identify attentive Portuguese

GNSS Stakeholders. This process was guided by a previous study8 led by RAND

Corporation, who develops research and analysis for the United States (US) Department

of Defense. This study includes a description of the US’ GPS Stakeholders which facilitated

the process of determining the Portuguese GNSS stakeholders.

After the stakeholder analysis process, an online questionnaire and open-ended

interview with the stakeholders was performed, to collect data from those who were

considered illustrative for a national representative picture. The sampling method that

was used for the Stakeholders selection was the non-probabilistic method9 which means

that each of them were selected based on previously chosen criteria and known

8 Scott Pace, et al., The Global Positioning System: Assessing National Policies, California, RAND Corporation,

1995, pp 11-44.

9 Hermano Carmo, Manuela Ferreira, Metodologia da Investigação, Guia da Auto-aprendizagem, 2ª Edição,

Lisboa, Universidade Aberta, 2008, pp 209-210.

4

probability is not guaranteed. The non-probabilistic method used was the typical case

sampling10 due to time limitations and also because the interviewees are intentionally

chosen due to sharing a common element. In this process of sampling, unique or special

cases may be included to bring authenticity to the study.

The online questionnaire was created based on closed questioning11, using control

questions12 and also using the Likert scale13. The software used was the open-source

software Google Forms. The interview type used was dominantly formal – an interview

with open questions14 to focus mostly on the interviewee’s knowledge. Both of the

stakeholder data collection methods: Inquiry by interview and Inquiry by questionnaire

have pros and cons. As a result, the information obtained makes both of these methods

complement each other.15 The whole process made it possible to find out what the

Portuguese GNSS stakeholders look for in a PNT system and also to construct an updated

picture of the PNT development in Portugal.

Finally, a GPS Jamming Trial was performed, using physical equipment to collect

GPS data and, also, to analyse the crew’s reaction when bound to a hostile environment.

Several guidelines were used to conduct a Case Study with Field Observations16, such as

prevision; first sight; additional preparation for the observation; additional

conceptualisation for the development; data collection and validation; data analysis and,

eventually, give the public a comprehension opportunity.17 This last aspect, made it

10 Hermano Carmo, Manuela Ferreira, p 216.

11 Ibidem, p 157.

12 Ibidem, p 158

13 Ibidem, p 160.

14 Ibidem, pp 146-148.

15 Ibidem, p 164.

16 Robert Stake, A Arte de Investigação com Estudos de Caso, Tradução de Ana Maria Chaves, Lisboa, Fundação

Calouste Gulbenkian, 2007, pp 68-70.

17 Ibidem, p 68-70.


5

possible to test whether the Portuguese Warships are prepared in the event of an

unexpected scenario.

Structure

This dissertation consists of an introduction, five content chapters and a

discussion.

● Introduction. Includes a brief description of the context, objectives, methodology

and structure of the dissertation.

● Chapter 1 – What are resilient PNT Systems? This chapter starts by defining

resilience, followed by a definition of PNT Systems and how they can be resilient.

Then, there is a brief explanation of PNT systems that are available or under

development.

● Chapter 2 – GNSS Vulnerabilities. This chapter portrays the vulnerabilities that

these systems are sensible to: interference, jamming and spoofing, among others.

Previous jamming and spoofing trials performed by other countries are also laid out

in this chapter.

● Chapter 3 – Study Methodology. This chapter explains the adopted methods,

namely for the process of data collection, results presentation and analysis.

● Chapter 4 – Results. This chapter presents all the data acquired in the online

questionnaire/personal interviews and also the data collected in the Jamming Trial.

● Chapter 5 – Analysis. This chapter comprises the discussions that were made after

processing the collected data.

● Chapter 6 – The Path for a Resilient PNT System in Portugal. This chapter shows an

updated Portuguese PNT picture and advises the measures that should be taken by

Portugal and the Portuguese Navy.

● Conclusion. This chapter shows a brief explanation of how the results were

obtained; the difficulties faced in data collection and improvements that could have

been made. A final suggestion for a future project is also presented.

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7

Chapter 1 – What are resilient PNT Systems?

1.1 What is Resilience?

“Resilience is a property intimately associated with the organisations’ capacity to

avoid, contain and mitigate accidents.”18 When it comes to having a resilient system, it

means it can deal with unexpected events or failures and catastrophes. Resilience cannot

be classified as a technical or organisational mean - if an organisation operates resilient

systems, then it is resilient too. Both concepts can be and are related.

Having a resilient system does not mean that it absolutely cannot fail – it means

that it somehow has a way to be back online by itself when submitted to a vulnerable

situation. This leads to the fact that a resilient system must instate both technology and

its operators but also be robust19, flexible20, redundant21, available22, precise23, accurate24

and continuous25.

Pedro Antunes and Hernâni Mourão, in their Resilient Business Project

Management Report described five key aspects that support system resilience, such as:

18Pedro Antunes, Hernâni Mourão, Resilient Business Process Management; Frameworks and Services, Lisbon,

Faculdade de Ciências da Universidade de Lisboa, 2011, p 2.

19Ibidem, p 5.

20Ibidem, p 5.

21International Maritime Organization (IMO), Resolution A.915 (22), Revised Maritime Policy and

Requirements for a Global Navigation Satellite System, IMO, 2001. p 9.

22Ibidem, p 6.

23Ibidem p 8.

24Ibidem, p 6.

25Ibidem, p 6.

8

Failure handling – “systems operate in heterogeneous, distributed and

autonomous platforms that are prone to component, communication and

system failures”26;

● Exception handling – “Unlike failures, which result from system

malfunctions, exceptions come from semantic discrepancies between the

actual organisational environment and the processes modelled by the

system”27;

● Model adaption - due to “incomplete developments, development errors

and changes in the business environment”28;

● Restricted Ad-hoc changes – “concern operations not predicted in the

process models and carried out during the execution phase to accomplish

work”29;

● Unstructured interventions - it should be already predicted that

“cascading”30 events might occur. The concept “cascading” can be defined as

“to occur in a sequence or successive stages”31. In this case, it means events

that consequently lead to the occurrence of others successively and without

warning. This may lead to a chaotic situation.

For GNSS, Alan Cameron believes that resilience goes way “beyond what we

normally think of as position and timing sensors”32. Cameron also gives us the concept

that PNT is much more than sensors complementing each other. It is more of a mixture of

26Pedro Antunes, Hernâni Mourão, p 6.

27Ibidem, p 7.

28Ibidem, p 8.

29Ibidem, p 8.

30Ibidem, p 9.

31The Free Dictionary by Farlex, http://www.thefreedictionary.com/cascading, (accessed on May 2017).

32Alan Cameron, “Resilient”, GPS WORLD, January Issue, 2016, p 6.


9

hardware and software, old and new data coming from sources that we do not even

regard as PNT sources. These sources could even be amateur applications.33

So how is it possible to monitor resilience? Firstly, there is a need to evaluate

whether and how do the systems adapt to different kinds of derangements. Rojier Woltjer

claims that to monitor resilience the following properties should be considered:

● Buffering capacity – “the size or kind of disruptions the system can absorb or

adapt to without a fundamental breakdown in performance”34;

● Flexibility - “the system’s ability to restructure itself in response to external

changes or pressures”35;

● The margin – “how closely or how precarious the system is currently

operating relative to one or another kind of performance boundary”36;

● Tolerance - “how a system behaves near a boundary”37, for instance if it loses

information quality or simple blacks-out;

● Cross-scale interactions – “the resilience of a system defined at one scale

depends on influences from scales above and below”38.

In order to be a High Reliability Organisation (HRO) – such as aviation and air traffic

companies, space exploration organisations, nuclear power plants – an organisation

needs to have resilient systems in order to be prepared for “blackouts”, system failure

and to quickly be back online. Why then, should the Portuguese Navy be a HRO? Firstly, a

HRO manages to keep going with their production and offer high reliability when

submitted to precarious, risky or calamitous conditions, without disturbing human lives

due to the designed and developed combination of men and technology, and

33Alan Cameron, “Resilient”, p 6.

34Erik Hollnagel, David Woods, Nancy Leveson, Resilience Engineering, Concepts and Precepts, Aldershot,

Ashgate Publishing Limited, 2006, p 23.

35Ibidem, p 23.

36Ibidem, p 23.

37Ibidem, p 23.

38Ibidem, p 23.

10

perpetuating the financial and environmental conditions. The Portuguese Navy should,

then, be a HRO as its main mission involves military operations that require fast and

effective responses and also taking responsibility in keeping maritime security. Operations

that involve saving human lives or dealing with dynamic, unpredictable and complex

operational contexts require a flexible and adaptive organisation with robust and resilient

systems that have the capability to react and keep going among unpredicted failures.

System resilience leads us to the concept of resilience engineering. David Woods

considers four leading concepts for resilience39 in resilience engineering:

● “Rebound from trauma and return to equilibrium”;

● “Synonym for robustness”;

● “Opposite of brittleness”;

● “Network architectures that can sustain the ability to adapt to future surprises

as conditions evolve”.

Woods also states that we are facing a technological problem nowadays, due to

interconnected networks of several systems that, when put to a single system failure, may

cause the whole network to be disrupted. This is why, in the last decade, a whole new

effort has been put into this concept of resilience. “The empirical progress has come from

finding, studying, and modelling the biological and human systems that are prepared to

handle surprises.”

As technology and society are in constant change and development, in order to

create a resilient system capable to respond to any kind of event, risk management cannot

be ignored and needs to be proactive. “Risk management in the present context is

directed towards control of the risk related to the dynamic course of events following a

disturbance of a potentially hazardous physical process.” Rasmussen claims that there is

a high risk in technology manufacturing, in the present, due to the fact that organisations

and companies are combining ancient management techniques with ultra-modern

39David Woods, Four concepts for resilience and the implications for the future of resilience engineering,

Columbus, The Ohio State University, 2015, p 1.


11

technology. For that reason, in order to perform a proactive risk management analysis

when developing a resilient and prosperous system, there are several types of accidents

with different risk management strategies40:

● Occupational safety – when a small but frequent accident occurs and is

controlled based on past accidents (empirical);

● Medium-sized accidents – lead to design improvement, as they are not so

frequent. Risk management is normally achieved by removing the accident

causes;

● Large-scale accidents – as they have a very low probability of occurring, risk

management cannot be empirical. This means a probabilistic analysis has to

be made in order to identify what events are mostly probable to occur and

identify their causes in order to remove them or upgrade the separate

systems to more resilient ones.

A resilient organisation must have safety as a key-value, because safety is reflected

on the failures that do not actually occur. One of the biggest flaws related to resilience

happens when a system seems resilient, and research and development tend to decrease,

as well as investment and maintenance budgets. The fact is, technology keeps changing

as well as unpredicted flaws may occur.

1.2 The path to PNT

1.2.1 Looking through GNSS

The United States were the first in developing one of the position and timing

reference systems and, in fact, the most commonly used one: the Global Positioning

System (GPS), a space-based radionavigation system. After the United States, some

interested countries started developing their own GNSS. Russia started developing

40Jens Rasmussen, Inge Svedung, pp 27-28.

12

GLONASS in the late 70s41, the European Union (EU) started developing GALILEO in 199942.

China more recently started developing BeiDou II Navigation Satellite System (BDS), which

aims to be totally launched by 202043. Japan and India also started developing their

Regional Navigation Satellite Systems (RNSS): Quasi-Zenith Satellite System (QZSS) and

the Indian Regional Navigation Satellite System (IRNSS), correspondingly. These countries

are trying to work on GNSS resiliency (by creating their own satellite systems for

redundancy) but not through offering a full solution as these systems work based on a

GPS-like technology with weak satellite signals, only operating in different compatible

frequencies.

As we know, GPS can offer accurate PNT information and is still the military’s

leading system. However, the information is not always available or reliable, but it is still

used by several ships’ equipment, as it can be seen in Figure 1, apart from the Global

Maritime Distress Safety System (GMDSS) that is also GPS-dependent and is missing in

Figure 1. If GPS by any chance fails, the actual equipment, or any other equipment that

depends on its information, fails to offer accurate data or any data at all.

Figure 1 - Ships’ equipment using GPS44

41Scott Madry, Global Navigation Satellite Systems and their Applications, New York, Springer Science +

Business Media LCC, 2015, p 45.

42Vincent Reillon, Briefing GALILEO: Overcoming obstacles, History of EU Global Navigation Systems, 2017, p

6.

43Shau-Shiun Jan, An-Lin Tao, Comprehensive Comparisons of Satellite Data, Signals, and Measurements

between the BeiDou Navigation Satellite System and the Global Positioning System, National Cheng Kung University, Taiwan, 2016, p 1.

44Paul Williams, Chris Hargreaves, “UK eLoran – Initial Operational Capability at the Port of Dover”, Proceedings of the 2013 International Technical Meeting of The Institute of Navigation, California, 2013, p 393.


13

GPS, in order to be constantly reliable and available, needs a software and

hardware redesign to be able to rapidly include or exclude different sensors and it should

also be compatible with all civilian and military needs.

How does GPS then work? It works by comparing the different signals with the

same codes that are broadcasted from each satellite and processing the timing difference

between them. Nowadays, normally at least four satellites are in view, and in that manner,

a more rigorous position can be determined, as the fourth satellite is essential for a 3D

position. With the intersection of four spheres, there is only one place in the world where

you can be at.45 However, if only three satellites are visible, a position still can be

determined making the assumption that the receiver is at the mean sea level.46

How can timing be so accurate, then? Each GPS satellite possesses incorporated

caesium and rubidium atomic clocks. For example, a caesium atomic clock works by

electrifying caesium atoms with microwave energy until they start vibrating. A caesium

atom has a frequency of 9,192,631,770 Hz47, the frequency of the vibration is then

measured and, it is used as a timing reference. “The second itself was defined by the

caesium atomic clock method in 1967, and it was in 1971 that International Atomic Time

(TAI) was defined”48.

In order to compute the exact time, it would be much simpler if each GPS receiver

possessed an atomic clock itself but, that, would be make each unit much more expensive,

so the receiver actually seizes the signals from minimum three satellites - for a two-

dimensional position and minimum four satellites for a three-dimensional position - in

view, processes the signal codes and measures its own clock error. This time will be the

one that the receiver will adopt. This process is a repetitive cycle.

45Scott Madry, pp 35-40.

46Integrated Mapping Ltd., How GPS Works, https://www.maptoaster.com/maptoaster-topo-

nz/articles/how-gps-works/how-gps-works.html, (accessed May 2017).

47United States Naval Observatory, Cesium Atoms at Work, http://tycho.usno.navy.mil/caesium.html,

(accessed October 2016).

48Scott Madry, p 35.

14

The GPS System provides two types of service: the Standard Positioning Service

(SPS) and the Precise Positioning Service (PPS), conceived for authorised military users.49

The PPS uses both L1 (1575.42 MHz)50 and L2 (1227.60 MHz)51 frequencies. The L1

and L2 frequencies contain a coarse/acquisition code (C/A-code) that is available for all

civil, commercial and military receivers and a Precision code (P-code) only for authorised

users. The P-code is cryptographically altered to become the Y-code and is not available

to those who do not have the cryptographic keys.52 The performance levels using the C/A-

code receivers are 5 – 10m accuracy, and using the P/Y-code receivers, 2 – 9 m.53

A new GPS generation is in development as “in 2014 Lockheed-Martin won the

contract for the new Block III satellites that will have a second civilian code, improved anti-

jamming capabilities, a stronger signal, more power, a new military code, and a

completely upgraded ground control segment.”54

Several systems have been created, since the development of GPS, to upgrade the

nature and accuracy of many civilian positioning systems. The Differential GPS, or DGPS,

uses various reliable fixed stations with known positions, which are compared to the

received GPS signal. The difference between these two positions is transmitted in almost

real time, constantly, by Low-Frequency (LF) radio waves to the surrounding GPS

receivers. Our position can be obtained then with a 0.7 – 3m accuracy (in C/A-code) and

0.5 – 2m (in P/Y-code)55. A considerable difference between DGPS and GPS is that, DGPS,

49Fisheries and Oceans Canada Coast Guard, Primer or GPS and DGPS, Canadian Coast Guard, 2000, p 7.

50European Space Agency Navipedia, GPS Signal Plan, 2011,

http://www.navipedia.net/index.php/GPS_Signal_Plan, (accessed June 2017).

51Ibidem.

52European Space Agency Navipedia, GPS Services, 2011, http://www.navipedia.net/index.php/GPS_Services,

(accessed June 2017).

53European Space Agency Navipedia, GPS Performances, 2011,

http://www.navipedia.net/index.php/GPS_Performances, (accessed June 2017).


55European Space Agency Navipedia, GPS Performances.


15

can send warnings to the users in case the system is unreliable (integrity monitoring)56. In

Portugal, there are currently four operational DGPS stations (Cabo Carvoeiro, Sagres,

Horta and Porto Santo) and a monitoring station in the Direção de Faróis (Paço de Arcos)57.

Despite the fact that ground-based rectification systems using DGPS are very useful, they

have the same vulnerabilities as GPS.

For this matter, Ground Based Augmentation Systems (GBAS) were created to

enhance GPS’ precision.58This system is of indispensable use in precision landings and

approaches. A GBAS Ground Facility consists, normally, of three GPS antennas, a

processing utility and VHF Data Broadcast transmitter. A user, in order to operate this

system, should have a Very High Frequency (VHF) Antenna.59 The GPS antennas that the

GBAS beholds are in known positions. The receivers measure the time that the signal takes

to travel from the GPS satellites to the antennas and calculate the distance. This calculated

distance is then compared to the actual known distance in order to determine the error.60

The GBAS Ground address has the capability to monitor the performance of the GPS

satellites which makes it possible to stop receiving signals from a certain satellite if that

its information is considered unhealthy.61 Space-Based Augmentation systems (SBAS)

have also been established and consist of:

“A ground infrastructure that includes the accurately-surveyed sensor stations which

receive the data from the primary GNSS satellites and a Processing Facility Centre

which computes integrity and corrections forming the SBAS signal-in-space (SIS).

56Fisheries and Oceans Canada Coast Guard, p 11.

57Luís Monteiro, Designing, configuring and validating the Portuguese DGPS Network, PhD Thesis through

Nottingham University, Nottingham, 2004.

58Federal Aviation Administration, Satellite Navigation – GBAS – How it works,

https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/laas/howitworks/, (accessed on March 2017).

59Federal Aviation Administration, Satellite Navigation – GBAS – How it works.

60Ibidem.

61Ibidem.

16

The SBAS Geostationary (GEO) satellites relay the Signal-in-space (SIS) to the SBAS

users which determine their position and time information.”62

The U.S. established its own SBAS: Wide Area Augmentation System (WAAS),

which provides real time and continental-scale augmentation. It was originally developed

and activated in 200363 because the civilian GPS signal did not meet the aviation

requirements, needing availability and better accuracy. This augmentation system

operates in North America but its coverage area lasts well into South America, the Atlantic

and the Pacific Oceans. There is still a separate SBAS, developed also by the U.S. only for

Military use and for encrypted P(Y) code receivers called the Wide Area GPS Enhancement

(WAGE).

There are other solutions apart from DGPS and SBAS that can increase GNSS’

performance, such as Real Time Kinematics (RTK) and Wide Area RTK (WARTK).

The Real Time Kinematics (RTK) is used when accuracy is needed by enhancing

GNSS’ information precision. Basically, the system reduces and removes errors from a

base and a rover station (station that collects data at remote locations64). Just like in any

other GNSS, the position is known by calculating ranges. “At a very basic conceptual level,

the range is calculated by determining the number of carrier cycles between the satellite

and the rover station, then multiplying this number by the carrier wavelength.”65 These

ranges still include errors that are eliminated by a system requirement including

measurement transmissions from the base station to the rover station.

The Wide Area RTK (WARTK) was developed in the 90’s and allows the

transmission of RTK services to a greater scale (greater than 100 kilometres between the

62European Space Agency Navipedia, SBAS Fundamentals,

http://www.navipedia.net/index.php/SBAS_Fundamentals, (accessed January 2017).

63GPS GOV, Wide Area Augmentation System (WAAS) Status and History, 2014,

http://www.gps.gov/multimedia/presentations/2014/09/ION/bunce.pdf (accessed December 2016).

64Althos, GPS ROVER STATION, http://www.wirelessdictionary.com/wireless_dictionary_GPS_Rover_

Station_Definition.html, (accessed January 2017).

65Novatel, Real-Time Kinematic, http://www.novatel.com/an-introduction-to-gnss/chapter-5-resolving-

errors/real-time-kinematic-rtk/, (accessed January 2017).


17

base and the rover stations). “The Wide-Area Real-Time Kinematics (WARTK) technique

for dual and 3-frequency systems are based on an optimal combination of accurate

ionospheric and geodetic models in a permanent reference stations network.”66 The only

reasons for the range of the WARTK being limited to few tens of kilometres, are the

differential ionospheric corrections made between the rover station and the closest GNSS

station. “The ionosphere produces ambiguity biases and correlations (…). Even with the

aid of multi-reference-station techniques (…) several thousand would be required to cover

such a service to the whole European region.”67

Russia began developing their space-based GNSS, “Globalnaya Navigatsionnaya

Sputnikovaya Sistema” (GLONASS) in 197668. Two major differences from GPS are that

GLONASS has its own atomic timing reference system and does not use the WGS84 datum

like GPS, using their own PZ-90 global reference system. Russia is developing – having

achieved partial operational status in 2011 – its own System for Differential Corrections

and Monitoring (SDCM) linked with GLONASS. The SDCM is different from other

augmentation systems, as it will administer integrity monitoring for both GLONASS and

GPS.

Europe decided to create its own GPS augmentation system known as the

European Geostationary Navigation Overlay Service (EGNOS), coming up, later on, with

the GALILEO project. Galileo was originally planned to be interoperable with GPS and

Russian GLONASS and will, when concluded, consist of 30 (24 satellites plus 6

spares)69Medium Earth Orbit (MEO) satellites, each possessing two Rubidium Atomic

66European Space Agency Navipedia, Wide Area RTK (WARTK),

http://www.navipedia.net/index.php/Wide_Area_RTK_ (WARTK), (accessed January 2017).

67European Space Agency Navipedia, Wide Area RTK (WARTK).


69Vincent Reillon, p 6.

18

Frequency Standard (RAFS) clocks and two Passive Hydrogen Maser (PHS) clocks70.

Galileo’s first in-orbit satellites (validation elements) were launched in 2005 and 200871.

On December 2016, it was inaugurated with 15 operational satellites out of 18 in orbit,

with an expected launch of more four satellites in November 2017.72 Full operational

capability is not expected before 202073.

GALILEO consists of an Open-Service (OS) with an availability of 99% and a Public

Regulated Service (PRS) with an availability of 99.5%.74

China, on the other hand, started developing its own GNSS, having three

operational satellites since the year 2000. A second generation of this system was then

developed and named Compass. Nowadays, China has a modernised version of Compass

– BeiDou II, which achieved operational capability since 2011. In 2015, this system

consisted of 14 satellites75, and was planned to be completely operable by 2020 (lately

hastened to 2017).

India developed a Regional Satellite System. The Indian Regional Navigation

Satellite System (IRNSS) consists of seven satellites with rubidium atomic clocks, in the

space segment. It is also part of India’s plans to create its own timing reference system

and SBAS: the GPS-Aided GEO Augmented Navigation System (GAGAN). This project was

developed by the Indian Space Research Organisation (ISRO), being operational for the

first time in 200876.

70European Space Agency, GALILEO clock anomalies under investigation, 2017,

http://www.esa.int/Our_Activities/Navigation/Galileo_clock_anomalies_under_investigation, (accessed May 2017).

71Vincent Reillon, p 4.

72Ibidem, p 8.

73Ibidem, p 8.

74European Space Agency Navipedia, GALILEO Performances, 2011,

http://www.navipedia.net/index.php/Galileo_Performances, (accessed June 2017).


76Ibidem, pp 51-52.


19

Japan, being the country with most GPS use for car navigation and other services77,

is not trying to develop its own GNSS, but has in the last decade made, just like other

countries, some efforts in order to solve problems related to the use of GPS in urban

canyon areas like the city of Tokyo. GPS signals can, sometimes, be reflected by tall

buildings in urban landscapes (creating multi-path interference) and, as they propagate,

positioning errors are generated. The Quasi-Zenith Satellite System (QZSS) started in 2002

and consists of three satellites, having its first launch in 2010 and was completed by 2013.

Its design makes it totally operable and redundant when operating with other GNSS. Japan

also has its own SBAS: the Japanese Multi-functional Satellite Augmentation System

(MSAS), developed in 2007 and consisting of two GEO satellites in order to work with GPS

and follow-on systems. 78

As conclusion place a summary of present GNSS signals in use. Look at the graphics

presented in: http://www.navipedia.net/index.php/GNSS_signal

1.2.2 What are PNT Systems?

The National Air and Space Museum Smithsonian Institution defines Position as

“determining your location”, Navigation as “finding your way from one place to another”

and Timing as “supplying highly accurate time to synchronise complex systems”.79

The PNT services are used by both civilian and military systems and were initially

created for military-use purposes. The development of the first PNT system – GPS –

started in the Sputnik era, after the first artificial satellite launched in 1957 by the Soviet

Union80. A few years later, in the 60s, the first satellite navigation experiments were

conducted by the United States’ (U.S.) Navy, with the intent to track submarines carrying

77Ibidem p 52.

78Ibidem, pp 52-55.

79National Air and Space Museum Smithsonian Institute, PNT (Positioning, Navigation and Timing), 2012,

https://timeandnavigation.si.edu/multimedia-asset/pnt-positioning-navigation-and-timing, (accessed March 2017).

80Scott Madry, p 4.

20

nuclear missiles. Between 1969 and 197081, Ivan Getting, president of the U.S.’ Aerospace

Corporation, recommended the creation of a commission to analyse the progress on

satellite navigation since it was an area that could be worked on and invested in.

Nowadays, there are several systems that share similar a similar complex satellite

configuration and architecture with GPS. Nevertheless, PNT systems concern much more

than just GNSS. These systems should provide rigorous positioning and timing information

and are part of the Global Positioning System-of-Systems (GPSS)82. The GPSS embraces all

elements - such as services, systems, components and applications83 that are useful to

worldwide users for constant PNT information update. The purpose of the GPSS is to make

sure that individual systems are compatible and, even though they can be operated

individually, complement each other in a more robust system.

In the last decade intense research and progress has been made in this area, with

the emergence of new innovative, intelligent and robust PNT systems that accommodate

various sensors and information sources.

1.2.3 Alternative PNT information sources

In 2004, the United States of America (USA) published a directive expressing the

need to develop a GPS backup expressing that the “continuing growth of services based

on the Global Positioning System presents opportunities, risks, and threats to the U.S.

national, homeland, and economic security”84. The USA also stated that effort should be

put into developing, deploying and operating new national security and public services or

81Steven Dick, Roger Launius, Social Impact of Spaceflight, NASA History Division, Washington DC, 2007, p

177.

82Jules McNeff, “Changing the Game Changer”, “The Way Ahead for Military PNT”, Inside GNSS,

November/December Issue, 2010, pp 47-48.

83Ibidem.

84National Security Presidential Directives, NSPD-39: U.S. Space-Based Position, Navigation, and Timing Policy,

2004.


21

upgrading the existent ones; and defining the requirements and their division between

the GPS and its augmentation systems.85

“More than 98% of the missiles currently in the U.S. arsenal have missions (…)

critically dependent on GPS for achieving the required level of delivery accuracy.”86 This

means that there is a need of cutting the GPS dependency, as it is vulnerable to jamming,

spoofing.

Sherman Lo, senior research engineer in the GPS Laboratory at Stanford University,

believes that the qualities that are mostly need in an Alternative Positioning, Navigation

and Timing (APNT) system are “robustness, integrity/authenticity, and accuracy (timing

and positioning)”.87 There is not, however, a consensus about how an APNT system should

be and what features it should have.

The General Lighthouse Authorities of the United Kingdom and Ireland (GLA) have

been pioneers in the maritime APNT research88, especially with the development of

enhanced-Loran. The Federal Aviation Administration has also developed their Distance

Measuring Equipment (DME) that is a “combination of ground and airborne equipment

which gives a continuous slant range distance-from-station readout by measuring time-

lapse of a signal transmitted by the aircraft to the station and responded back”89. The

Department of Homeland Security itself is looking into enhanced-Loran and Defence

Advanced Research Projects Agency (DARPA) is developing chip-scale inertials.90

85National Security Presidential Directives

86Andrei Shkel, Expert Advice: The Chip-scale Combinatorial Atomic Navigator, http://gpsworld.com/expert-

advice-the-chip-scale-combinatorial-atomic-navigator/, (accessed December 2016).

87Sherman Lo, “Alternative PNT: Assured Service, GNSS Backup”, Inside GNSS, September/October Issue,

2015, pp 32-33.

88Ibidem.

89Skybrary, Distance Measuring Equipment (DME),

http://www.skybrary.aero/index.php/Distance_Measuring_Equipment_(DME), (accessed March 2017).

90Sherman Lo, pp 32-33.

22

Sherman Lo, also affirms that the solution does not go through developing or

acquiring several systems due to the cost but “fewer solutions will allow us to focus on

the security of each solution rather than just counting on security through diversity”.91

The LORAN-C system used to work for the forty-eight U.S.’ continental states,

coastal areas and some parts of Alaska until the year of 201092, when the signal was

terminated93. This system used to deliver radionavigation service for U.S. coastal waters

and provided position, navigation and timing services for both civil and military air, land

and marine users.

E-LORAN itself was developed from LORAN-C as feedback from the 2001 Volpe

Report94 on GPS Vulnerability. This report concentrated on the fact that the United States,

just like other countries, were starting to depend only on GPS and declared it as vulnerable

to intentional or unintentional interference.95

The main difference between eLORAN and the LORAN-C is the innovative

introduction of a new data channel on the signal that is transmitted, allowing enhanced

corrections, more accurate information transmitted to the receiver and optional

warnings. This difference is responsible for its possible use on aircraft landing and marine

navigation on harbour approaches, especially with low-visibility conditions.

Originally, e-LORAN was created by Ursanav as a navigation service using the

previous LORAN-C transmitter stations at a high power level with a 100kHz frequency, but

now offering bigger “accuracy, integrity, availability and continuity”96 than LORAN-C ever

offered. A particular aspect of these 100 kHz low-frequency transmissions is that they can

91Sherman Lo, pp 32-33.

92United States Coast Guard Navigation Center, Loran-C General Information,

http://www.navcen.uscg.gov/?pageName=loranMain, (accessed October 2016).

93Office of Management and Budget, Budget of the U.S. Government: Fiscal Year 2010, U.S.A, 2010, p 40.

94John A. Volpe National Transportation Systems, Vulnerability Assessment of the Transportation

Infrastructure relying on the Global Positioning System, Final Report, Massachusetts, 2001.

95International Loran Organisation, Enhanced Loran (e-Loran), Definition Document, 2007, p 7.

96Charles Curry, Delivering a National Timescale using eLORAN, Chronos Technology, Lydbrook, 2014, p 5.


23

actually penetrate through buildings in order to be used indoors (one of GPSIII’s

ambitions), only by using a particular object – H-field antenna (magnetic antenna).

Chronos Technology, GLA, the United Kingdom’s National Physical Laboratory and

Ursanav have been partners since 2011 in the e-LORAN development research project.97

Throughout these years, several aspects have been looked at. One of them is the

propagation speed of the e-LORAN signals. The speed is higher over seawater98 so it is

easier to know the time delay due to the actual propagation through the atmosphere –

this delay is known with great precision. Nevertheless, the propagation over land is slightly

slower because there is a bigger signal delay, known as the Additional Secondary Factor

(ASF). The ASF can reach a significance of several microseconds. All the existing e-LORAN

stations have their ASF predicted by using a computing model, due to the different values

of the earth’s conductivity that lead to the signal’s attenuation (and varies in different

planet regions). This ASF value is measured instantly when the timing receiver is firstly

operated, which means that it can vary with the seasons or atmospheric conditions. For

that reason, the eLORAN Differential Time Receiver (EDTR) was used, so that corrections

can be made and sent to the receiver by the new operational LORAN Data Channel (LDC).

Figure 2 shows the difference of three different parameters (Accuracy, Integrity

and Availability) between LORAN-C and eLORAN.

Figure 2 - Generations of Loran's performance99

97Charles Curry, Delivering a National Timescale using eLORAN, p 5.

98Ibidem, p 7.

99General Lighthouse Authorities of the United Kingdom and Ireland, “Briefing note: Evolution from Loran-C to eLoran”, p 3.

24

When eLORAN is used for positioning, at least three stations are needed

(calculating a two-dimensional position fix and time). Nevertheless, additional stations

offer bigger information accuracy.

Differential eLORAN, consists of an eLORAN receiver equipped with an external H-

field antenna. It was developed with the intention of improving the positioning’s accuracy

with ASF corrections. In order to have full Differential eLORAN service for harbour

approach and entrance, there must be at least three eLORAN transmitters close to the

harbour as well as a Differential eLORAN Reference Station that can make the respective

variable ASF correction that can occur due to seasonal, daily or weather variations.

Some countries are making an effort to implement eLORAN technologies or to

upgrade their obsolete LORAN-C equipment. South Korea is one of the countries investing

in the eLORAN system due to the GPS jamming incidents that it has been suffering in the

past few years. Figure 4 shows a table of actually known and confirmed incidents that they

suffered.

Figure 3 - Korean jamming incidents100

South Korea’s eLORAN initial implementation plan consisted in upgrading their old

LORAN-C stations to eLORAN; building three new eLORAN stations; and having forty-three

100General Lighthouse Authorities of the United Kingdom and Ireland, “Briefing note: Evolution from Loran-C

to eLoran”, p 3.


25

differential eLORAN stations that would cover the whole country with 20m accuracy101.

This initial plan was improved to a new “Revised Korean e-LORAN Plan”102 that consists in

two-phase access: the first phase consisted in implementing maritime e-LORAN for the

west sea of Korea by the end of the year 2015 (which still is not completed and should

only be so by the end of 2019103) and if it turns out to be useful and reliable, expand it by

implementing more transmitters and differential stations (second phase).104

In 2014 there were nine Northern European available eLORAN stations (one in the

United Kingdom (Anthorn), Germany (Sylt) and Denmark (Faroe Islands)), two in France

(Lessay and Soustons) and four in Norway (Vaerlandet, Boe, Jan Mayen and Berlevag), all

used in Prototype e-LORAN mode)105. The Netherlands declared their first differential

eLORAN implementation in the Port of Rotterdam, in December 2015, which uses signals

from France, Germany and the United Kingdom106.

In the end of 2016, France lost interest and shut down its stations. Norway also

lost interest stating that it is “outdated and has very few users”107and Denmark will lose

the French financial support on its Faroe Island transmitter108. This means that if these

eLORAN sites are completely erased, it will be hard to continue an implementation plan

101Federal Aviation Administration, The Global Loran/eLoran Infrastructure Evolution, A Robust and Resilient

PNT Backup for GNSS, USA, 2014, p 31.

102Ibidem.

103Japan Times, “South Korea revives GPS backup project after alleged jamming by North Korea”, 2016,

http://www.japantimes.co.jp/news/2016/05/02/asia-pacific/south-korea-revives-gps-backup-project-after-alleged-jamming-by-north-korea/#.WAVG1eArLIV, (accessed October 2016).

104Federal Aviation Administration, The Global Loran/eLoran Infrastructure Evolution, p 32.

105Ibidem, p 20.

106Dee Ann Divis, “Proposal for U.S. eLoran Service Gains Ground”, 2014,

http://www.insidegnss.com/node/3853, (accessed October 2016).

107 Royal Institute of Navigation, “UK eLoran abandoned”, 2016, https://www.rin.org.uk/NewsItem/4433/UK-

eLoran-abandoned, (accessed May 2017).

108 Charles Curry, GPS-Free UTC TimeScale Using eLoran, International Timing and Sync Forum 2015,

Edinburgh, 2015, p 15.

26

and the United Kingdom’s station will only be able to provide timing – limited in a way –

as positioning will not be possible without trilateration.109

The U.S., on the other hand, are still in the process of dismantling its old LORAN-C

stations instead of investing in upgrading them to e-LORAN, for GNSS redundancy. As said

by the Office of Management and Budget, on 2010’s financial year budget, “the Nation no

longer needs this system because the federally-supported civilian Global Positioning

System has replaced it with superior capabilities”110.

It is hard for the United States to take a position or make any statement when

Europe is falling back from this project. As said by Professor David Last, “the question is

whether we are going to have an Eastern Europe with a clear fall-back to an eLORAN-type

(e-Chayka) system, and Western Europe switching theirs off”.111 He also pointed out that

what Europe actually needs is to see that the U.S. are also interested in eLORAN: “the U.S.

are very influential, and if the U.S. are going to stand up and say, ‘We’re bringing eLORAN

back’ — that in itself would be a very powerful message”112.

One of the countries that deserves emphasis is the United Kingdom due to the

great effort that Chronos Techonology has been putting in the eLORAN implementation

plan. Chronos has been responsible for the GNSS Availability Accuracy Reliability and

Integrity Assessment for timing and Navigation (GAARDIAN Project) and the GNSS Services

Needing Trust in Navigation, Electronics, Location & Timing (SENTINEL Project). The

United Kingdom has its eLORAN system operating with GPS since May 2010.113 In 2010,

Chronos and GLA analysed the existing options in order to provide resilient PNT and to

109David Last, “U.S. Nears eLoran Decision with Broad International Implications”, Washington View – Inside

GNSS, March/April Issue, 2015, pp 24-31.

110Office of Management and Budgets, Terminations, Reductions, and Savings, Budget of the U.S.

Government, Washington D.C., 2009.

111David Last, pp 24-31.

112Ibidem.

113Paul Williams, David Last, Nick Ward, The Deployment of eLoran in the UK, General Lighthouse Authorities

of the United Kingdom and Ireland, Harwich, 2013, p 1.


27

follow IMO’s advice on the adoption of an e-Navigation strategy.114 The research

developed by GLA led to the conclusion that the implementation of eLORAN would allow

the reduction of the Aids-to-Navigation (AtoN) infrastructure and the removal of some

lights and physical aids. This would reduce the yearly overall costs.

Another alternative PNT information source is Inertial Navigation. “Inertial

Navigation is a self-contained navigation technique in which measurements provided by

accelerometers and gyroscopes are used to track the position and orientation of an object

relative to a known starting point, orientation and velocity”.115 It is also a basic form of

navigation and consists on knowing your initial position, velocity and orientation and then

measuring your orientation changes and acceleration, without relying on external

references. Inertial sensors themselves, measure the rotation rate and acceleration using

gyroscopes and accelerometers, respectively. Normally, three orthogonal rate-

gyroscopes and three orthogonal accelerometers make an Inertial Measurement Unit

(IMU).116

An Inertial Navigation System normally consists of an IMU, Instrument Support

Electronics and Navigation Computers to integrate and maintain the position estimate.117

The IMU itself can have two types of configurations: Strapdown Systems or Stable

Platform Systems. The Strapdown Systems as the actual name says, have their sensors

rigidly attached to the device. This reduces the cost and, also, the mechanical complexity.

The Stable Platform Systems have the inertial sensors mechanically isolated from

rotational motion and installed in a stable platform. This method is widely used when high

accuracy is needed, mostly in ships and submarines. These systems can also be called

Gimbaled Inertial Platforms and normally three of them are needed to protect a system

from three axes rotations: roll, pitch and yaw.

114International Maritime Organisation, Subcommittee on the Safety of Navigation, Report to the Maritime

Safety Committee, IMO, 2011, p 18.

115Oliver Woodman, An Introduction to Inertial Navigation, 2007, p 5.

116 Tampere University of Technology, Basic Principles of Inertial Navigation,

http://aerostudents.com/files/avionics/InertialNavigationSystems.pdf, (accessed December 2016).

117 Ibidem

28

The advantages of Inertial Navigation Systems are that they do not need external

references (only an initial position) and are autonomous; they are immune to jamming

and spoofing and do not need any antenna that can be radar detected (important in a

warfare scenario), unlike other PNT Systems. On the other hand, the error increases with

time (as the only real position is the first one); high acquisition and maintenance costs

compared to GPS; and higher power requirements than GPS.118

In the beginning of 2017, DARPA started developing a vibration and shock-tolerant

inertial sensor that, they believe, will mitigate the need of GPS. This project, named ATLAS,

“will deliver a comprehensive approach to breaking performance and cost, size, weight

and power barriers in inertial sensor technology that prevent robust, GPS-independent,

military positioning, navigation and guidance”119. The project consists in making a

combination of a micro-electro-mechanical systems with a Coriolis Vibratory Gyroscope

which can be seen in Figure 4 below.

Figure 4 - Micro-electro-mechanical System Coriolis Vibratory Gyroscope120

Nevertheless, there is a big engineering challenge within that consists in creating

a whole new system architecture that can transfer the stability from the atomic time

reference to the Coriolis Vibratory Gyroscope without increasing the Signal-to-Noise Ratio

(SNR).

118Tampere University of Technology.

119GPS WORLD, “HRL Labs to develop inertial sensor tech for DARPA”, GPS WORLD, 2017,

http://gpsworld.com/hrl-labs-to-develop-inertial-sensor-tech-for-darpa/, (accessed January 2017).

120Paul Buckley, “Next-gen inertial sensors aim to replace GPS”, Smart2zero, 2016, http://www.smart2zero.com/news/next-gen-inertial-sensors-aim-replace-gps, (accessed July 2017).


29

DARPA is focusing on reducing the GPS reliance by providing redundant

capabilities and designing new PNT solutions. Some of their main goals include creating

ultra-stable clocks and providing PNT systems in new environments such as indoor,

underwater and underground, where GPS is not capable of providing fixing solutions. To

achieve these goals, DARPA started a project in 2012 named Chip-Scale Combinatorial

Atomic Navigator (C-SCAN).121 The final product of this project should be a small IMU that

brings atomic and inertial sensors together in a microsystem, with a very high motion

detection, combining both gyroscopes and accelerometers, designed in order to provide

more accurate and precise inertial navigation, in a very small and scrupulous way.

Pseudolites are, also another PNT alternative, according to the Federal Aviation

Administration APNT Research Program122. Having its use been recommended since late

70’s and early 80’s123, the term Pseudolites comes from the merging of the two terms

“Pseudo” and “Satellites”. A very important demonstration took place in the White Sands

Missile Range (a military testing area in New Mexico) in 2011124 with the support of

DARPA. Although Pseudolites are satellite-like transmitters (with a transmitter and a

receiver just like GNSS), they have their signals transmitted much closer to earth than GPS

satellites. To determine the location, the transmitter, which has an anti-jam antenna,

sends a signal to a modified GPS receiver which makes a range measurement.

Pseudolites use several geographical separate terrestrial transmitters to offer

passive pseudo ranging signals.125 There are several intrinsic benefits like unlimited user

capacity and, also, the possibility of transmitting signals from different equipment, like a

Distance Measuring Equipment (DME) or a Ground Based Transceiver (GBT), reducing the

number of terrestrial stations needed. The total travel time of the signal can be calculated

121Andrei Shkel, “The Chip-scale Combinatorial Atomic Navigator”, GPS WORLD, August Issue, 2013, pp 8-10.

122Sherman Lo, Pseudolite Alternatives for Alternate Positioning, Navigation and Timing (APNT), p 1.

123Cillian O’Driscoll, Daniele Borio, Joaquim Fortuny, Scoping Study on Pseudolites, European Commission Joint Research Center, 2011, p 1.

124Kathryn Bailey, Moving Celestial To Terrestrial: Leveraging Pseudolites For Assured PNT,

http://www.cerdec.army.mil/news_and_media/Moving_celestial_to_terrestrial_leveraging_pseudolites_for_Assured_PNT/, (accessed December 2016).

125Cillian O’Driscoll, Daniele Borio, Joaquim Fortuny, p 1.

30

using the signal’s Time of Arrival (TOA), more specifically, from the time difference

between transmit time indicated by the ground clock and received time measured by the

user clock. Nevertheless, the clock synchronization to the ground clock must be known.

Three stations are needed for passive ranging but, as said above, the use of DME and GBT

may reduce station need.

The Satellite Time and Location (STL) Service, developed by Iridium

Communications Inc., consists of 66 cross-linked, low-earth orbit satellites.126 This

technology can be included in several types of devices, as it is chip-size, and can make it

much harder to spoof or jam GPS receivers operating this system. STL also has a unique

code for each ground position which makes the system only usable if the user is in the

right and expected position. Some of the advantages of this service are that it is already

in space, tested and ready to use; its low earth orbit satellites allow a significate stronger

signal than GPS (which is much harder to jam); it is independent to any other technology

and it will also be supported by Iridium NEXT (next-generation global satellite generation)

supposed to be concluded at the end of 2017.127

The Network Time Protocol (NTP) was developed by Professor David L. Mills, at the

University of Delaware in 1985.128Since then, NTP has been used as an online protocol for

time synchronization on computers and Local Area Networks and, also, an alternative for

time reference. Atomic clocks are the most reliable timing devices, but can be very

expensive. NTP synchronizes, using UTC as reference time129, to a reliable timing source:

it could be an actual computer, a watch or even an atomic clock in a GPS satellite.130 This

system selects the best available time source, which means, more sources lead to smaller

126GPS WORLD, “Iridium launches alternative GPS PNT service”, GPS WORLD, 2016,

http://gpsworld.com/iridium-launches-alternative-gps-pnt-service/, (accessed January 2017).

127GPS WORLD, “Iridium launches alternative GPS PNT service”.

128Richard Williams, What is NTP, http://www.galsys.co.uk/time-reference/basic-ntp/what-is-ntp.html,

(accessed March 2017).

129NTP FAQ, What is NTP?, http://www.ntp.org/ntpfaq/NTP-s-def.htm#AEN1259, (accessed March 2017).

130Richard Williams.


31

errors. Also, it identifies and excludes senseless time sources.131 If the network connection

is, somehow, temporarily unavailable the NTP uses past measurements to predict the

actual time and possible error.132

The Automatic Identification System (AIS) is commonly used in marine navigation

as it has the capability of transmitting diverse information like speed, course, position

(obtained from a GNSS receiver)133. The fact that the position is obtained by a GNSS

receiver aboard, makes this system GNSS dependent. “The Automatic Identification

System Autonomous Positioning System (AAPS) is comprised of a master AIS base station,

some slave base stations, a shipborne AIS equipment and an ASF correction system.”134

The time synchronization of the system is assured by the intercalary transmission of the

base station and the slave base stations, which signals are received by the AIS equipment

aboard and, posteriorly, an ASF correction system leads to better positioning accuracy by

reducing propagation errors. 135. It is possible to have autonomous positioning on the AIS

by measuring VHF radio signals from the actual base stations to the AIS equipment. “In

the AAPS, the AIS base stations are time synchronized. The shipborne AIS can measure

the transmission delay of the VHF AIS signal from the AIS base stations.” Then, it is possible

to know a vessel’s true position (calculated through the signal’s travelling time).136

Multisensor navigation is, also, a resilient alternative for PNT information as GNSS,

alone, cannot respond to various factors that have been referred throughout this study137.

131NTP FAQ.

132Ibidem.

133Qing Hu, Development of an Automatic Identification System Autonomous Positioning System,

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4701297/, (accessed March 2017).

134Ibidem.

135Qing Hu.

136Ibidem.

137Grejner-Brzezinska, et al., “Multisensor Navigation Systems: A Remedy for GNSS Vulnerabilities?”,

Proceedings of the Institute of Electric and Electronics Engineers, Vol. 104 nº 6, June 2016, p 1342.

32

Although a big effort has been made in the last decade to create new resilient PNT

alternatives, little effort has been made to bring them together.138

Multisensor navigation can be obtained by coupling several sensors together in

order to build a resilient, available and robust system. An example of several sensors that

already exist and could be brought together in a car navigation system, can be seen on

Figure 5 below.

Figure 5 - Multisensor navigation for a car navigation system139

There are two basic solutions to complement GNSS’ information: supervising the

received GNSS signal and/or adding other sensors’ data. This can be possible through a

Receiver Autonomous Integrity Monitoring (RAIM) technology that, other than integrating

all the positioning solutions, also can acquire and recognize system failures. Nevertheless,

RAIM is signal dependent for positioning determination, which means it is not a PNT

solution. 140

The systems presented above are some of the PNT alternatives that are already

being used in several countries or still in development and implementation. A general

knowledge about these systems should be known in order to adopt a resilient PNT

strategy through redundancy or upgrading the already existent systems.

138Alan Cameron, “A long look at advanced Multisensor Navigation and Positioning”, GPS WORLD, 2014,

http://gpsworld.com/a-long-look-at-advanced-multisensor-navigation-and-positioning/, (accessed July 2017).

139Ibidem. 140Grejner-Brzezinska, et al., p 1343.


33

1.2.4 How to seek resilience in a PNT System?

The GNSS when used for positioning, navigation and timing can have serious flaws

due to the distance of the actual satellites to the receivers. The signal’s power is very low

and vulnerable to interference, ionospheric effects, jamming and spoofing141. Jamming

and Spoofing cannot be anymore declared as rare events as it is becoming easier and

easier, every day, to acquire jamming and spoofing equipment online. The year of 2017

was marked by the release of the Pokémon Go game. Common players were jailbreaking

their phones and managing to fake GPS positions so they could complete the game

without having do wander through the streets. This is spoofing and it is possible to be

achieved in just about 90 seconds.142

Atmospheric effects are also very important to consider. “Space weather disturbs

the ionosphere to an extent where the model no longer works and large pseudo range

errors, which can affect position and timing, are generated”.143

Apart from the flaws that were referred, GNSS also has segment errors that can

also generate user problems. In 2014, incorrect ephemeris data was uploaded in the

Russian GLONASS satellites, causing positioning, navigation and timing information issues

for about half a day.144

When developing or implementing a new PNT system, the main objective should

be to “ensure the highest levels of data integrity”145 and for that reason “the underlying

141The Royal Academy of Engineering, Global Navigation Space Systems: reliance and vulnerabilities, London,

2011, p 8.

142Gohub, “In 2017, GPS Spoofing is the real bane of Pokémon GO, 2017”, https://pokemongohub.net/2017-

gps-spoofing-real-bane-pokemon-go/, (accessed May 2017).

143GPS WORLD, “Make it real: Developing a test framework for PNT systems and devices”,

http://gpsworld.com/make-it-real-developing-a-test-framework-for-pnt-systems-and-devices/, (accessed January 2017).

144Ibidem.

145McMurdo, Resilient PNT, At the Core of Mission Critical Applications,

http://www.mcmurdogroup.com/company/orolia-group/what-is-resilient-pnt/, (accessed May 2017).

34

PNT technologies, products and systems must be resilient.” For that reason, according to

the International Maritime Organisation (IMO), a resilient PNT system should have the

following functionalities or characteristics146:

● Serve general navigation (including harbour entrances and approaches);

● Be compatible with local augmentation (if this item is not already provided);

● Unlimited number of users;

● Low user cost;

● Should operate with geodetic and time reference systems;

● Provide the user with position, time, course and speed over ground

information;

● Inform the users when system degradation occurs;

● Be compatible with other shipborne equipment (Electronic Chart Display

Information System (ECDIS), Automatic Identification System (AIS), GMDSS

to offer them vessel data;

● Accuracy - “The degree of conformance between the estimated or measured

parameter of a craft at a given time and its true parameter at that time.”147

● Availability - “The percentage of time that an aid, or system of aids, is

performing a required function under stated conditions.”148

● Continuity– “The probability that, assuming a fault-free receiver, a user will

be able to determine position with specified accuracy and is able to monitor

the integrity of the determined position over the (short) time interval

applicable for a particular operation within a limited part of the coverage

area.”149

146International Maritime Organisation, Resolution A.915(22), Revised Maritime Policy for a Future Global

Navigation Satellite System, 2011, pp 68-79.


Navigation Satellite System, p 71.

148Ibidem, p 71.

149Ibidem, p 71.


35

● Integrity monitoring – “The process of determining whether the system

performance (or individual observations) allow use for navigation

purposes.”150

● Integrity risk – “Integrity risk. The probability that a user will experience a

position error larger than the threshold value without an alarm being raised

within the specified time to alarm at any instant of time at any location in the

coverage area.”151

● Redundancy – “The existence of multiple equipment or means for

accomplishing a given function in order to increase the reliability of the total

system.”152

● Reliability on its observations – “A measure of the effectiveness with which

gross errors may be detected. This internal reliability is usually expressed in

terms of marginally detectable bias.”153

Another way of seeking the resilience of a PNT System is by improving the existent

ones. The United States’ Department of Homeland Security did a report on the

improvement of the operation and development of GPS. Throughout this report they

referred several means to improve the resilience of equipment receiving GNSS signals154,

such as:

● Employing Obscure antennas155 – not visible from public access areas or

physically hiding the antennas (ex: plastic fencing);

150International Maritime Organisation, Resolution A.915(22), p 73.


Navigation Satellite System, p 71.

152Ibidem, p 74.

153Ibidem, pp 74.

154United States Department of Homeland Security, Improving the Operation and Development of the GPS

Equipment Used by Critical Infrastructure, United States Department of Homeland Security, 2017, pp 5-7.

155Ibidem, p 5.

36

● Employing Decoy antennas156 – using clear visible antennas in a public access

area far from the actual antenna;

● Wisely selecting antenna locations157 – installing the antenna from and

above (at least 10 meters) close structures for a great multipath environment

with an unobstructed sky-view;

● Blocking antennas158 – protecting the receiver from interference, jamming

and spoofing;

● Implementing redundancy159 – have two or three antennas in different

locations with different receivers for outputs comparison;

● Calibrating160 – evaluating the delay variations;

● Steering clear from low elevation signals161 – they are attenuated from

horizon-nulling antennas (below 25º degrees elevation);

● Using position hold for stationary timing receivers162 – timing receivers that

operate in position hold, needing only information from one satellite for

timing information;

● Using high-quality devices163 - timing receivers should have an atomic clock

as backup. Positioning can be backed up by inertial systems;

● Adding a sensor/blocker164 – sensors that detect jamming, spoofing or

interference and report to monitoring sites, also collecting this data for

156United States Department of Homeland Security, p 5.

157Ibidem, p 5.

158Ibidem, p 5.

159Ibidem, pp 5-6.

160Ibidem, p 6.

161Ibidem, p 6.

162Ibidem, p 6.

163 Ibidem, p 6.

164 Ibidem, p 6.


37

investigation. The blocker can also block radiofrequency inputs when one of

these events is detected;

● Practicing cyber hygiene165 - GNSS receivers and data processors are

computers that should have firewalls, anti-virus software and authentication

with strong passwords.

165United States Department of Homeland Security, pp 6-7.

38


39

Chapter 2 – GNSS Vulnerabilities

2.1 Vulnerabilities

There are several GPS sources of errors, per example:

Errors in the ephemeris data transmission (ex: in the transmission of the

satellite’s location) – this error is the difference between the expected and

actual position of the satellite166;

Satellite clock errors – although atomic clocks are accurate there isn’t

perfectly accurate synchronization between the timing of the satellite

broadcast signals and the GPS system time167;

Ionospheric effects that cause pseudorange correction errors which will be

referred further on in this section;

Multipath errors caused by reflected signals on the antennas – signals don’t

always travel straight to the antenna as they can be reflected by obstacles,

which makes antennas receive direct and reflected signals168 ;

Errors of the actual receiver (clock synchronisation with satellites, thermal

noise and software accuracy)169.

These sources of errors make GNSS systems vulnerable. Also, intentional or

unintentional events like Interference; Scintillation; Jamming and Spoofing may occur.

In January 2016, many GPS satellites broadcasted timing errors for a period of

nearly 12 hours. The United Kingdom’s Space Agency and the Royal Institute of Navigation

166How GPS works, http://www.how-gps-works.com/glossary/ephemeris-error.shtml, (accessed July 2017).

167Bharati Bidikar, et. al., “Satellite Clock Error and Orbital Solution Error Estimation for Precise Navigation Applications”, Scientific Research, 2013, p 23.

168Trimble, Trimble GPS Tutorial - Error Correction, http://www.trimble.com/gps_tutorial/howgps-error2.aspx, (accessed July 2017).

169Civil Engg Dictionary, Sources of errors in GPS, http://www.aboutcivil.org/sources-of-errors-in-gps.html, (accessed July 2017).

40

developed a report about this incident and concluded that the cost of GNSS disruption

can reach 1 billion pounds sterling per day. The report focuses on “ten application

domains in the United Kingdom (UK): Road, Rail, Aviation, Maritime, Food, Emergency and

Justice Services, Surveying, Location-Based Services (LBS), Other Infrastructure, and Other

Applications.”170

In this report, an important upshot was presented, according to the January 2016

incident: “A day in the UK without GNSS”. The most important facts, which were felt by

normal user citizens, are summarized in Table 1.

170Alan Cameron, “Double trouble: GNSS over-reliance and its costs”.


41

“A day in the UK without GNSS”

At home Most activities are not affected (apart from the

morning run and weather forecast).

On the move

Journey must me memorized/paper maps; More vehicles on the road (taking slower to consult

paper maps); On trains, there is not information on the next

departure; Queue on the phone line for calling cabs (app does

not work).

With others Not possible to track children; Friends no longer share their location; Augmented reality games do not work.

At the shops

Supermarket shelves run out of products; People hoard products and higher priced black

market may emerge; Delivery of online shopping loses efficiency.

When things go wrong

More time handling emergency calls; First responders (police, ambulance and fire services)

cannot use location to navigate to an incident; Lone works loses the safety that someone is able to

support them.

Back at home The groceries or take-away food is delayed. Table 1 – Impact of "A day in the UK without GNSS"171

2.1.1 Interference

Interference occurs when unwanted signals interfere with actual GNSS signals

leading to the loss of accuracy or even denying system function.172 This occurs due to the

weakness of the signals that can be up to a hundred times weaker than the background

noise. Also, even though the GNSS bands are protected, there are many signals being

transmitted in close frequencies and those, sometimes, cause interference.173 Normally,

some part of the background noise can be removed as well as similar signals that get

171Innovate UK, The UK Space Agency, The Royal Institute of Navigation, Economic Impact of a disruption to

GNSS, Showcase Report, London, London Economics, 2017, p 6.

172Septentrio Satellite Navigation, GNSS Interference, Belgium, 2012, p 3.

173Ibidem, p 4.

42

spilled on the GNSS bands, but some still manage to persist. An example of possible

interference is that the GLONASS L2 band shares some frequencies with radio amateur

bands. This can lead to temporary losses of GNSS signals in some countries. “A source of

interference is likely to affect multiple signals in the same GNSS band and may entirely

block reception of a whole GNSS band.”174

2.1.2 Ionospheric effects

GNSS signals pass through the Ionosphere until they reach the earth’s surface

receivers. There are free ionosphere electrons that have been separated from

atmosphere atoms through the sun’s ultraviolet light.175 In the night period, as there is so

sunlight, these electrons tend to reunite with the atoms. GNSS signals, on their way to the

earth’s surface, can be refracted by these electrons changing their travelling path and

speed. Although this process is important and must be taken into account in order to

maintain GNSS accuracy and availability, there is another important occurrence:

scintillation. “Scintillation occurs when irregularities in the electron density of the

ionosphere cause rapid changes in the phase and amplitude of the transmitted signals.”176

This factor may lead to the loss of the GNSS signals, as they will be ignored by the receivers

due to the different signal characteristics.

Normally, the sun’s radiation and ionization process is quite constant, which

makes it possible to correct most measurements and keep high accuracy. Nevertheless,

there can be sporadic sun storms that lead to an enormous increase of electrons in the

ionosphere. This phenomenon, as it happens occasionally, is difficult to predict and may

lead to the temporary loss of GNSS information.177

174Septentrio Satellite Navigation, p 5.

175Richard Langley., “Innovation: GNSS and the Ionosphere”, GPS WORLD, 2011, http://gpsworld.com/innovation-gnss-and-ionosphere-11036/, (accessed May 2017).

176Richard Langley.

177Ibidem.


43

2.1.3 Jamming and jamming trials

“Jamming devices are radio frequency transmitters that intentionally block, jam,

or interfere with lawful communications, such as cell phone calls, text messages, GPS

systems, and Wi-Fi networks.”178

As there is a considerable distance between the GPS’ satellites and the earth’s

surface, they are easy to jam. A GPS jammer can send its own signals on the same

frequency than the GPS bands, increasing the SNR and, consequently, preventing the GPS

receiver from receiving any signals. GNSS jamming devices can be mostly divided in two

categories: GPS only and GPS and mobile communications. Jammers - of both categories

- can be bought for less than a hundred dollars, depending on its power, and are

considered illegal to market, sell or use in the United States of America.179

There are several ways of protecting against jamming such as using Radio

Frequency (RF) filters on the receiver (if the jamming signal overpowers the GPS signal

and falls right in-band, it still might not be the best method); using IMU’s as said before;

using multiple antenna arrays with various directions in order to acquire signals from

multiple directions (to prevent from being affected by the effective range of the jamming

signals)180; using a Controlled Radiation Pattern Antenna (CRPA) that consists in an

antenna array and processing unit that phase-destructs (nulls) any interfering signals. A

CRPA consists of seven patches, each one with a low-noise amplifier and two filters for

out-of-band rejection. 181. The last and probably to most effective way, is investing in new

PNT alternatives that are not vulnerable to jamming.

178GPS.GOV, Information About GPS Jamming, http://www.gps.gov/spectrum/jamming/, (accessed January

2017).

179Ibidem.

180Novatel, Understanding the Difference Between Anti-Spoofing and Anti-Jamming, http://www.novatel.com/tech-talk/velocity/velocity-2013/understanding-the-difference-between-anti-spoofing-and-anti-jamming/, (accessed January 2017).

181GPS WORLD, “Anti-jam Protection by Antenna”, 2013, http://gpsworld.com/anti-jam-protection-by-antenna/, (accessed June 2017).

44

The SENTINEL Project Report on GNSS vulnerabilities enumerated several jamming

mitigation techniques such as giving more importance to resilient timing (by using Oven

Controlled Oscillators, Rubidium Clocks and Chip Scale Atomic Clocks) which preserves

accurate timing in a GPS-denied environment; the use of multiple GNSS has also been a

troubled option as nearly all the GNSS share the same or similar frequencies apart from

the Russian GLONASS182; and at last, having been referred before, implementing e-LORAN,

that may be up to a future shutdown.

In the Portuguese Navy, more specifically, no internal doctrine could be found,

throughout this research, of which antennas should be used or how they should be

positioned aboard. This means that if an assessment on this matter is made, it is possible

to find out in which way they antennas be less vulnerable to interference depending on

their type and where they should, originally, be installed.

Several jamming trials have been taken before and after the SENTINEL Project in

three different places. The first one took place in Sennybridge (Wales), the second one in

Nuneaton (England) and, the third, in Sweden.

The Sennybridge jamming trial was the first non-military trial using civilian

jammers, divided by three sessions: June 2011, June and October 2012 and 2015. One of

the conclusions that was extracted from these trials was that the Portable jammers’

effective range was much larger than what the sellers predicted.

The Nuneaton trial took place, mainly, to test the CTL3520, a hand-held jamming

detector, which was a 100% successful. The jammer was placed in a car boot. The car was

quickly identified and the jammer equipment was removed. The CTL3520, developed by

the University of Bath in the United Kingdom for the SENTINEL Project, is capable of

searching and finding the direction of a jammer, operating on the GPS L1 band.183

The Swedish Trial was, also, mainly performed to test the CTL3520’s direction

finding capability.

182Charles Curry, Sentinel Project, Report on GNSS Vulnerabilities, Chronos Technology, Lydbrook, 2014, p 31-

33.

183Ibidem, p 34.


45

In 2015, during the Annual Navigation Warfare trial hosted by the United Kingdom

Ministry of Defence, several GPS equipment and GANDALF MkII - a jammer detector -

were tested. GANDALF MkII estimates the jamming signal’s Direction of Arrival. If this

process is done several times, the true position of a jamming source can be identified as

well as it helps the operator find out which type of jammer is being used.184

In April 2008, the GLA in partnership with the United Kingdom Government’s

Defence Science and Technology Laboratory performed a jamming trial near Flamborough

Head (near the North Sea), using the vessel NLV “Pole Star”.The objectives and results of

this trial are described on table 2185 below.

Table 2 - Table 2 - NLV "Pole Star" Jamming Trial Results

184North Atlantic Treaty Organization, Testing direction finder at GPS Jamming Trials,

https://www.ncia.nato.int/NewsRoom/Pages/160905-Sennybridge-GPS-Jamming-Trials.aspx, (accessed January 2017).

185General Lighthouse Authorities of the United Kingdom and Ireland, GPS Jamming Trial, Executive Summary Report for Website, United Kingdom, 2008, p 4-5.

Objectives Results

Test GPS denial impact on maritime safety

The vessel was able to navigate using radar and traditional navigation techniques.

How mariners cope with GPS information loss

Loss of GPS caused many alarm sounds on the bridge (chaos).

How DGPS is affected by GPS Jamming

DGPS station in Flamborough Head was affected by GPS jamming (station went “unhealthy” and

as the alarms went off, locked up).

Test e-LORAN as a GNSS back-up system

e-LORAN service was not affected.

Effect of GPS Jamming on Automatic Identification

System (AIS)

GPS jamming affected the AIS (lost range and bearing information) and the nearby Maritime Coastguard Agency received erroneous data.

Effect on synchronized light units and systems

If there is GPS denial when they are first turned on, they fail to synchronize. Once synchronized they use their internal clock (synchronises with

GPS every 20 minutes).

Effect of GPS denial on communications systems

Digital Selective Calling (DSC) kept working through jamming periods yet failed to offer

accurate positioning information. Communication systems worked continuously.

46

Several conclusions were taken by the GLA from this trial such as:

GPS having great impact on maritime safety;

During a jamming trial the Vessel Traffic Service (VTS), obtains erroneous

vessel positioning data (such as vessels travelling over land);

If AIS is used as an AtoN, it can broadcast incorrect information which can be

completely dangerous for maritime safety;

In ships DSC emergency communications can be lost if they are based on

GPS;

The loss of GPS information can have a very big impact on mariner’s as they

will have to firstly identify the problem, secondly, be familiar with more

rudimental navigation techniques in order to always now the vessel’s

position and at last, have the ability to keep calm as alarms sounding on the

bridge can be a “stress” factor.186

In 2009, another Jamming Trial was taken by the GLA, but this time in Newcastle-

Upon-Tyne187 and using another vessel: THV “Galatea”. This time, when the jamming

signal was low no alarms sounded. However, there was absurdly erroneous positioning

and speed information. As the jamming signal was intensified, alarms started to sound on

the bridge until the Electronic Chart Display System (ECDIS), the Autopilot, the DGPS, the

DSC, the Radar, the Gyro-compass and the AIS failed completely.188

2.1.4 Spoofing and spoofing trials

Spoofing can be achieved through a complex signal generator that recreates

signals from various GPS satellites. Firstly, knowing the actual true position, this signal is

186General Lighthouse Authorities of the United Kingdom and Ireland, GPS Jamming Trial, p 5-6.

187Alan Grant, Paul Williams, Sally Basker, “GPS Jamming and its impact on maritime safety”, Port Technology International, 2010, pp 39-41.

188George Shaw, et al., Mitigating the effects of GNSS Interference – GLA monitoring and update on eLoran, General Lighthouse Authorities of the United Kingdom and Ireland, 2011, p 9.


47

transmitted to a GPS receiver189 . When the receiver accepts this signal it is possible to

simulate positions. These signals should be strong enough to prevail against true GPS

signals but not too strong to be ignored and originate system failure. This makes it harder

to discover when a spoofing attack occurs as there is no system failure and the receiver is

actually accepting the signals. Nevertheless, a slight drift of position over a long period

can lead to an accident.

It is, hard to spoof a military GPS as it contains an encrypted binary code, the Y-

code. This code is changed millions of times every second, not repeating for a period of at

least a week. It is nearly impossible to generate it without having the actual encryption

key.190 On the other hand it is much easier to spoof a civil GPS receiver because it uses the

open C/A-code that can be found on a public interface. 191

There are two ways of being protected against spoofing. The first and more

effective one, is by using a GPS receiver that contains a Selective Availability Anti-Spoofing

Module (SAASM), which means, that it uses the Y-code. Nevertheless, only government

authorized users can acquire these devices. The second way, which is open to public use,

is by using a multi-constellation receiver that uses signals from GPS, GLONASS, BeiDou

and Galileo. It is much harder to spoof signals coming from all these different frequency

transmitters.192

In 2011, Iran claimed to be responsible for making a Lockheed Martin drone crash

in Iranian territory and, in January 2016, two U.S. Navy Patrol Boats entered the Iranian

waters, being intercepted and captured. Investigation about these two cases is still in

development, but it is believed that it could have been spoofing attempts that changed

the track of the U.S.’ drone and patrol boats.193

189Novatel, Understanding the Difference Between Anti-Spoofing and Anti-Jamming.

190Ibidem.

191Ibidem.

192Ibidem.

193Mark Psiaki, Todd Humphreys, Protecting GPS From Spoofers Is Critical to the Future of Navigation, http://spectrum.ieee.org/telecom/security/protecting-gps-from-spoofers-is-critical-to-the-future-of-navigation, (accessed January 2017).

48

Then how is spoofing really done? On civilian receivers, as said before, it is easily

achieved. Knowing the exact position, you will be at the start of the spoofing session, the

process starts. On that position, it is possible to find out which satellites will be in view,

based on the satellites’ ephemeris data. Given that, the spoofer calculates each satellite’s

Pseudo Random Noise (PRN) code using formulas that are available on a public database.

Then, the spoofer sends out signals with the same codes as the satellites in view, which

are accepted by the receivers as being part of the strongest true GPS signals. Finally, the

hardest part is to drown the true signals by increasing the spoofing power until the

receiver accepts them. Nevertheless, it is important (for the system not to fail and for the

attempt to be disguised) to not increase the signal’s power too much. Once the spoofed

signals attach to the receiver, it can be adjusted leaving the actual true GPS signals behind

and forgotten.194

In 2012, one year after the Lockheed Martin drone’s crash disaster, the U.S.

Department of Homeland Security decided to test if it was possible to attack a helicopter

drone. For that matter, The University of Texas, more specifically Professor Todd

Humphreys and his research team, prepared a trial at the White Sands Missile Range. They

managed to complete the task of making the helicopter drone land - and nearly crash in

the sand - by spoofing the GPS signals. The spoofed GPS signals kept telling the drone that

is was ascending, which made it correct its position by pointing towards land.

In 2013, again, the University of Texas and Professor Todd Humphreys, organized

a spoofing trial involving the vessel White Rose of Drachs. “The purpose of the experiment

was to measure the difficulty of carrying out a spoofing attack at sea and to determine

how easily sensors in the ship's command room could identify the threat”.195 The trial took

place 30 miles off the coast of Italy, while the vessel travelled from Monaco to Rhodes, in

Greece. Two students managed to take control of the ship’s navigation system by

overpowering the GPS signals. There was no sound of alarms, which made the situation

194Mark Psiaki, Todd Humphreys.

195UTNews, “UT Austin Researchers Successfully Spoof an $80 million Yacht at Sea”, 2013, https://news.utexas.edu/2013/07/29/ut-austin-researchers-successfully-spoof-an-80-million-yacht-at-sea, (accessed January 2017).


49

seem normal. As the team had total control of the ship’s navigation systems they managed

to change its course. Nevertheless, all that was seen on the electronic chart was a straight-

line due to the course corrections that were being made but, in reality, they were

gradually pushing away the ship from its actual track. After all the manoeuvres, under the

spoofing attack, had been made, the ship turned out to be hundreds of meters away from

the supposed electronic chart track.196

196UTNews.

50


51

Chapter 3 – Methodology

3.1 Resilience analysis

According to the definitions of resilience that were previously referred, a resilience

assessment was made to all the Organisations that were studied throughout this project.

In order to analyse if the Organisations (and systems they depend on or supply)

being studied in this project are working towards resilience, the following concepts had

to be considered:

Reconceptualization197 – Does the Organisation approach the system’s

design problem in anticipation? Does it consider the need to change?

Studying what goes right198 – Do they consider studying what we consider

everyday as “just happens”?

Cultivating requisite imagination199 – Do they anticipate failure before it

occurs?

Developing new tools to develop and operate systems200 – do they to

develop tools to help the systems control and adapt themselves?

Creating ways to monitor the development and occurrence of unforeseen

situations201 – do their systems make adjustments and respond to

unforeseen situations?

197Christopher Nemeth, Erik Hollnagel, Becoming Resilient, Resilience Engineering in Practice Volume 2,

Ashgate Publishing Limited, Farnham, 2014, p xiii.

198Ibidem, p xiii.

199Ibidem, p xiii.

200Ibidem, p xiv.

201Ibidem, p xv.

52

Cultivating ways to visualize and foresee side effects202 – Do they create ways

for systems to show how they adapt? Do they consider the interaction

between systems and how cascading events may occur?

Promoting and using great design203 – do they give importance to good

design as it can mitigate several issues?

Acknowledging and managing variability204 – do they embrace non-linear

approaches in order to explore how systems and networks adapt?

When we talk about system resilience it is, almost, inevitable to refer the Systems-

Theoretic Accident Modelling and Processes (STAMP)205 approach by Nancy Leveson. This

model considers safety and resilience as control problems and, includes:

Approaches to accident investigation/analysis;

Hazard analysis;

Accident prevention;

Risk assessment;

Risk management;

In the STAMP approach, accidents are seen, not only because of component

malfunction, but also as results of improper processes due to206:

Interactions between societies, people or organisational structures;

Engineering activities;

System components;

Poor safety control on the system’s creation, design, construction and

operation.

202Christopher Nemeth, Erik Hollnagel, p xv.

203Ibidem, p xv.

204Ibidem, p xvi.

205Erik Hollnagel, David Woods, Nancy Leveson, Resilience Engineering, Concepts and Precepts, Ashgate Publishing Limited, Farnham, 2006, pp 96-107.

206Ibidem, p 97.


53

This model, inspired the data analysis of this project, as it offers theoretical

foundation to develop important tools for project managers in order to assist them in risk

management and building resilient systems. The three STAMP fundamental concepts can

be seen on Figure 6 below. The absence of control on these concepts can lead to

accidents.

Figure 6 - STAMP fundamental concepts207

(1) Constraints – systems are viewed as hierarchic structures, in which, each

above level implies constraints to the level below. “Accidents result from

inadequate enforcement of constraints on behaviour (e.g., the physical

system, engineering design, management, and regulatory behaviour)”208.

(2) Levels of control – between these levels need to be communication channels

in order to send the constraints information to the levels below and a

measuring channel for sending feedback (status reports, risk assessments,

etc.).

(3) Process models – must contain the system’s current state; relationship

required between the different variables; and in which ways the process can

change. Accidents often occur when there is a discrepancy between the

process model and the actual process state.

207Nancy Leveson, A New Accident Model for Engineering Safer Systems, Massachusetts Institute of

Technology, Massachusetts, 2004, pp 12-13.

208Erik Hollnagel, David Woods, Nancy Leveson, pp 99.

STA

MP Constraints (1)

Levels of control (2)

Process models (3)

54

This approach considers the following procedures and advices (that are implied in

Leveson’s theory)209:

Definition of the task that is being analysed (define the objective and

boundaries);

Data collection (ex: accident and enquiry reports);

Construction of the Hierarchical control structure (based on the data

collection process);

Bad control analysis (identification of the control failures);

Review and Analysis (creation of a report).

STAMP makes it possible to analyse hazards and create techniques in order to

prevent them when accidents are not – only - a consequence of component failure. These

techniques lead to building more resilient systems as they are more prepared against

operation-error accidents, human or organisational-caused accidents.

In this project, the resilience assessment to the organisations was made through

data collection by Interviews (Online questionnaire and Open Interview) and, in the

Portuguese Navy, more specifically, through GPS Jamming Trials - considered as a possible

“accident”.

3.2 Stakeholder analysis

In order to perform a stakeholder analysis and find out which individuals or

organisations depend on PNT systems for achieving their daily objectives and

organisational goals, an American study210 led by RAND Corporation was used. This study

includes a description of the US’ GPS Stakeholders which eased the process of determining

the Portuguese GNSS stakeholders. Nevertheless, Portugal does not have exactly the

209Nancy Leveson, pp 25-30.

210Scott Pace, et al., The Global Positioning System: Assessing National Policies, California, RAND Corporation, 1995, pp 11-44.


55

same organisations or individuals, which required an adaptation process and the creation

of selection criteria. The stakeholders were chosen throughout the following steps211:

1st step: Identifying which is the main theme: PNT Systems;

2nd Step: Defining which groups or individuals depend or share interest in this

theme: Users (Positioning, Navigation and Timing); GNSS Services Suppliers;

GNSS-dependent Services Suppliers, Academia, Investigation, Control and

Vigilance Authorities; and Regulating Authorities;

3rd step: Identify how many individuals or organisations exist according to

the previously defined groups.

Naturally, a stakeholder analysis should answer the following questions212:

What are the current and future interest of these stakeholders in the use and

management of this theme?

How do they use it?

How do they benefit from it?

What are their rights and responsibilities towards the main theme?

Which are the networks and organisations they take part in?

How willingly are they to participate in this theme’s management?

Which are the human, technical and financial resources that they are willing

to give out for managing this theme?

The final Stakeholder groups that were identified were:

Users (for Positioning purposes);

Users (for Navigation purposes);

Users (for Timing reference purposes);

Investigation;

Academia;

211Károly Futaki, Danube Flood risk Project, Stakeholder Selection Strategy, VKKI, Budapest, 2010, p 9.

212Károly Futaki, p 11.

56

GNSS Services Suppliers;

GNSS-dependent Services Suppliers;

Regulating Authorities;

Control and Vigilance Authorities.

Also, in order to identify, which stakeholders were indispensable for the

development of this project, an analysis of the Potential stakeholders213 was made,

according to their importance, and can be seen on Table 3 below.

Primary

Stakeholders

Secondary

Stakeholders

Key

Stakeholders

GNSS-dependent Services

Suppliers

GNSS Services Suppliers

Academia

Users

Regulating Authorities

Control and Vigilance

Authorities

Table 3 – Primary, Secondary and Key Stakeholders

Primary Stakeholders are considered “Beneficiaries or targets of the effort”214;

Secondary Stakeholders are considered “the ones whose jobs or lives might be affected

by the process or results of the effort”215; Key stakeholders are “Government officials and

Policy makers”216.

After the Stakeholders Identification was concluded, a research of these

representatives in Portugal was made and, then, Organisations and Individuals were

contacted through e-mail – APPENDIX A. The ones who replied were asked to answer to

an online questionnaire and an Open Interview.

For the Online Questionnaire, Google Forms was used as a web open-source

application for data collection. The data analysis nevertheless, could only be statistically

213Phil Rabinowitz, Section 8. Identifying and Analyzing Stakeholders and Their Interests,

http://ctb.ku.edu/en/table-of-contents/participation/encouraging-involvement/identify-stakeholders/main, (accessed June 2017).

214Ibidem.

215Ibidem.

216Ibidem.


57

analysed by groups of stakeholders, as some groups had only one representative

stakeholder. The quantitative analysis of the Online Questionnaire responses was made

in Microsoft Excel, and results presented in several diagrams.

At last, the Open Interview, through voice recording, was analysed through the

MAXQDA 12 software that makes it possible to code pre-defined words or phrases that

are considered important. When all the interviews were coded, it was possible to see the

elements that were shared between each Organisation - or individual representing an

Organisation - and possible solutions that were presented – and sometimes similar. These

results can, also, be seen in Chapter 4.

3.3 Resilience in operations – Jamming Trial

In order to assess the PNT resilience in the Portuguese Navy, three jamming trials

were performed aboard a Portuguese Warship. These trials were theoretically based on

two previous jamming trials performed by the GLA that - described in Chapter 2. They

helped to predict what could happen, in the worst perspective.

For this project’s trials two distinct models of jammers were acquired for

redundancy – as there was no guarantee any of them would work. During the trials, data

was extracted from the Ship’s Master device directly to a computer, and was parsed with

open sourced script from http://freenmea.net/dashboard#/files,.

Initially, a schedule was elaborated in order to be compatible with the ship’s

operational commitment. The schedule can be seen on Table 4 below.

58

Phases Objectives

Preparation

(In harbour)

Investigate previous international Trials;

Visiting the ship in order to evaluate what systems it had and test

data extraction to a personal computer;

Material preparation (video recorder, jamming devices, Spectrum

Analyzer (R&S FSH3), Computer, R232 Cable);

Briefing for the Ship’s Commander in order to explain the

objectives of the study and Trial

1st Trial

Test the crew’s reaction in a hazardous environment (alarms

sounding on the bridge and system’s unavailability);

Evaluate systems’ reactions

Are there any back-ups?

2nd Trial

No surprise factor – after the first trial the crew already knew

what was happening;

Systems’ reactions to GPS information denial;

Video record Procedures for digital proof;

3rd Trial

No surprise factor anymore - after the first trial the crew already

knew what was happening;

Systems’ reactions to GPS information denial;

Video record Procedures for digital proof;

Table 4 - Trial Schedule

Nevertheless, there was one difference between the jamming trial led on this

project and the ones led by the GLA: the “surprise factor”. This item is very important for

evaluating part of the Organisation’s resilience and could not be tested. The fact that the

three jamming trials were performed during the same period aboard made it impossible,

as the crew members soon realized what was happening.


59

In order to perform a vulnerability assessment, an event sheet was created in

order to keep redundancy on data recording (and register other details that could not be

recorded). It was used in every trial and can be seen on Figure 7.

Figure 7 - Trial event sheet

60


61

Chapter 4 –Results

4.1 Portuguese PNT Stakeholders point of view and needs

4.1.1 Online Questionnaire

In the stakeholder enquiry through the online questionnaire, 15 questions were

chosen (2 out of these 15 questions referred to demographic data to identify which

organisation they worked for or who they were). Personal information was treated

confidentially and was not used for any statistic purpose. The template can be found in

APPENDIX B.

The online questionnaires were analysed by grouping the stakeholders, according

to their own classification (some stakeholders considered themselves to be part of more

than one group).

The Investigation stakeholders believe they are quite dependent on GNSS

(mean=7.5 on a scale from 0 to 10); largely dependent on GNSS for Positioning

(mean=8.75 on a scale from 0 to 10); averagely dependent on GNSS for Navigation

(mean=5.63 on a scale from 0 to 10) and even less dependent for timing information

(mean=4.88 on a scale from 0 to 10). Also, they do not consider their organisation totally

prepared in case of GNSS unavailability (mean=3.13 on a scale from 0 to 10) but, a large

part of them, stated that their organisations have backup systems in case of GNSS

unavailability (62.5%). The parameters that the investigation stakeholders considered

vital for responding to their daily service needs are Precision, Coverage, Accuracy,

Availability and Integrity (14.6% each). Nevertheless, GPS is not the only system they use.

Other systems were referred: DGPS, EGNOS, GALILEO, WAAS, GLONASS, BeiDou, PPP,

even though they consider rather important for other GPS complementing systems to be

adopted and implemented in Portugal (mean=8 on a scale from 0 to 10). When asked their

opinion about what solution should be implemented to augment GPS’ performance, the

most common answer was the implementation of local systems (ex: Pseudolites) (62.5%).

62

At last, these stakeholders believe that the Portuguese population’s knowledge of PNT

systems is below average (mean=3.63 on a scale from 0 to 10).

The users (for Navigation purposes) believe they are quite dependent on GNSS

(mean=7.44 on a scale from 0 to 10); largely dependent for Positioning (mean=8.25 on a

scale from 0 to 10); considerably dependent on GNSS for Navigation (mean=6.56 on a

scale from 0 to 10) and also on GNSS for timing information (mean=6.88 on a scale from

0 to 10). Also, they consider their organisation averagely prepared in case of GNSS

unavailability (mean=5.13 on a scale from 0 to 10) and, most of them, stated that their

organisations have backup systems in case of GNSS unavailability (62.5%). The parameter

that they considered vital for responding to their daily service needs is Availability (15%).

Nevertheless, GPS is not the only system they use. Other systems and services were

referred: DGPS, EGNOS, GALILEO, WAAS, GLONASS; though they consider rather

important for other GPS complementing systems to be adopted and implemented in

Portugal (mean=8.06 on a scale from 0 to 10). When asked their opinion about what

solution should be implemented to augment GPS’ performance, the most common

answer was the implementation of local systems (ex: Pseudolites) (37.5%). At last, these

stakeholders believe that the Portuguese population’s knowledge of PNT systems is below

average (mean=3.43 on a scale from 0 to 10).

The users (for Positioning purposes) stakeholders believe they are quite

dependent on GNSS (mean=7.44 on a scale from 0 to 10); largely dependent for

Positioning (mean=8.11 on a scale from 0 to 10); averagely dependent on GNSS for

Navigation (mean=5.76 on a scale from 0 to 10) and also considerably dependent on GNSS

for timing information (mean=6.11 on a scale from 0 to 10). Also, they consider their

organisation averagely prepared in case of GNSS unavailability (mean=5.05 on a scale

from 0 to 10) but, most of them, stated that their organisations have backup systems in

case of GNSS unavailability (70%). The parameter that they considered vital for responding

to their daily service needs is Availability (15.7%). Nevertheless, GPS is not the only system

they use. Other systems and services were referred: DGPS, EGNOS, GALILEO, WAAS,

GLONASS; even though they consider rather important for other GPS complementing


63

systems to be adopted and implemented in Portugal (mean=7.30 on a scale from 0 to 10).

When asked their opinion about what solution should be implemented to augment GPS’

performance, the most common answer was the implementation of local systems (ex:

Pseudolites) (35.3%). At last, they believe that the Portuguese population’s knowledge of

PNT systems is below average (mean=3.47 on a scale from 0 to 10).

The users (for Time Reference purposes) believe they are dependent on GNSS

(mean=7 on a scale from 0 to 10); largely dependent for Positioning (mean=7.8 on a scale

from 0 to 10); considerably dependent on GNSS for Navigation (mean=6.2 on a scale from

0 to 10) and largely dependent for timing information (mean=7.5 on a scale from 0 to 10).

Also, they consider their organisation averagely prepared in case of GNSS unavailability

(mean=5.4 on a scale from 0 to 10) but most of them stated that their organisation has

backup systems in case of GNSS unavailability (70%). The parameter that they considered

vital for responding to their daily service needs is Availability (17%). Nevertheless, GPS is

not the only system they use. Other systems and services were referred: DGPS, EGNOS,

GALILEO, GLONASS, WAAS; even though they consider rather important for other GPS

complementing systems to be adopted and implemented in Portugal (mean=7.6 on a scale

from 0 to 10). When asked their opinion about what solution should be implemented to

augment GPS’ performance, the most common answer was the adoption and training of

complementary navigation methods (ex: Celestial Navigation) (50%). At last, these

stakeholders believe that the Portuguese population’s knowledge of PNT systems is below

average (mean=3.9 on a scale from 0 to 10).

The Control and Vigilance Authorities consider themselves dependent on GNSS

(mean=7.6 on a scale from 0 to 10); largely dependent for Positioning (mean=7.8 on a

scale from 0 to 10), largely dependent on GNSS for Navigation (mean=7 on a scale from 0

to 10) and for timing information (mean=7.6 on a scale from 0 to 10). Also, they consider

their organisation prepared in case of GNSS unavailability (mean=8 on a scale from 0 to

10) but, all of them, stated that their organisation has backup systems in case of GNSS

unavailability (100%). The parameter that they considered vital for responding to their

daily service needs is Precision, Accuracy and Availability (14.8% each). Nevertheless, GPS

64

is not the only system they use. Other systems and services were referred: DGPS, EGNOS,

GALILEO, GLONASS, AIS; even though they consider rather important for other GPS

complementing systems to be adopted and implemented in Portugal (mean=7.8 on a scale

from 0 to 10). When asked their opinion about what solution should be implemented to

augment GPS’ performance, the most common answer was the adoption and training of

complementary navigation methods (ex: Celestial Navigation) and investment in regional

and local differential systems (ex: DGPS, WAAS, etc.) (40%, each). At last, these

stakeholders believe that the Portuguese population’s knowledge of PNT systems is way

below average (mean=1.8 on a scale from 0 to 10).

The Academia Stakeholders believe they are dependent on GNSS (mean=8 on a

scale from 0 to 10), largely dependent for Positioning (mean=9 on a scale from 0 to 10),

averagely dependent on GNSS for Navigation (mean=5.25 on a scale from 0 to 10) and a

little less dependent for timing information (mean=4.75 on a scale from 0 to 10). Also,

they consider their organisations considerably prepared in case of GNSS unavailability

(mean=6 on a scale from 0 to 10) but, all of them, stated that their organisations have

backup systems in case of GNSS unavailability (100%). The parameter that they considered

vital for responding to their daily service needs is Continuity, Integrity, Availability and

Accuracy (14.3% each). Nevertheless, GPS is not the only system they use. Other systems

and services were referred: DGPS, EGNOS, GALILEO, GLONASS, WAAS; even though they

consider rather important for other GPS complementing systems to be adopted and

implemented in Portugal (mean=8 on a scale from 0 to 10). When asked their opinion

about what solution should be implemented to augment GPS’ performance, the most

common answer was the use of local systems (ex: Pseudolites) (50%). At last, these

stakeholders believe that the Portuguese population’s knowledge of PNT systems is way

below average (mean=2.25 on a scale from 0 to 10).

The GNSS-dependent services suppliers consider themselves GNSS-dependent

(mean=8.5 on a scale from 0 to 10), largely dependent for Positioning (mean=9.5 on a

scale from 0 to 10), considerably dependent on GNSS for Navigation (mean=6.75 on a

scale from 0 to 10) and also for timing information (mean=6.25 on a scale from 0 to 10).


65

Also, they consider their organisations averagely prepared in case of GNSS unavailability

(mean=5.25 on a scale from 0 to 10) and, most of them, stated that their organisations

have backup systems in case of GNSS unavailability (75%). The parameter that they

considered vital for responding to their daily service needs is Availability and Continuity

(16% each). Nevertheless, GPS is not the only system they use. Other systems and services

were referred: DGPS, EGNOS, GALILEO, GLONASS, WAAS, BeiDou, PPP; even though they

consider rather important for other GPS complementing systems to be adopted and

implemented in Portugal (mean=7.25 on a scale from 0 to 10). When asked their opinion

about what solution should be implemented to augment GPS’ performance, no

conclusions can be taken as all the answers were different. At last, these stakeholders

believe that the Portuguese population’s knowledge of PNT systems is below average

(mean=3.25 on a scale from 0 to 10).

The GNSS services suppliers, included in this study, believe they are dependent on

GNSS (mean=8.4 on a scale from 0 to 10), largely dependent for Positioning (mean=8.8 on

a scale from 0 to 10), considerably dependent on GNSS for Navigation (mean=6.8 on a

scale from 0 to 10) and also for timing information (mean=6 on a scale from 0 to 10). Also,

they consider their organisation’s preparation below average in case of GNSS

unavailability (mean=4.4 on a scale from 0 to 10) but, most of them, stated that their

organisations have backup systems in case of GNSS unavailability (60%). The parameter

they considered vital for responding to their daily service needs is Availability and Integrity

(16.7% each). Nevertheless, GPS is not the only system they use. Other systems and

services were referred: DGPS, EGNOS, GALILEO, GLONASS, WAAS, BeiDou, PPP; even

though they consider rather important for other GPS complementing systems to be

adopted and implemented in Portugal (mean=7.4 on a scale from 0 to 10). When asked

their opinion about what solution should be implemented to augment GPS’ performance,

the most common answer was the implementation of local systems, like “Pseudolites”

(40%). At last, these stakeholders believe that the Portuguese population’s knowledge of

PNT systems is below average (mean=3.6 on a scale from 0 to 10).

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Only one Regulating Authority; Cartography Producer; Web Applications

Developer; Security; and Geodesy, Topography and Hydrography, stakeholders were

interviewed, which means, no conclusions can be stated.

As general results, including all stakeholders, it could be stated most consider

themselves GNSS dependent; mostly used GNSS systems are GPS, DGPS, GLONASS,

GALILEO AND EGNOS; most of the Stakeholders consider themselves quite dependent to

GNSS but, averagely prepared in case of GNSS unavailability. This can be seen on Figure 8

below. The remaining graphs that were used for results presented in this chapter can be

found in APPENDIX C.

Figure 8 - General questionnaire results


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4.1.2 Open interview

All the interviews made were transcript and coded. The most common topics, shared

by nearly all the interviewees, can be seen on Figure 9. After the most common topics

were identified, a Mind Map was created using the Software VUE in order to associate

these topics with the groups of stakeholders that referred them. The Full Mind Map can

be found on APPENDIX E. Then, an analysis of each most common topic was made in order

to take conclusions from the open interviews.

The most common topics that were referred by all the stakeholders interviewed,

were:

Efficiency;

Resilience;

Redundancy;

Costs;

Necessary GNSS characteristics;

Vulnerability;

Solutions presented;

GNSS dependency;

Alternatives.

Several solutions and alternatives were presented and can be seen on Figure 10

below. Other screenshots from the Mind Map - based on the results of the Personal

Figure 9 - Commons topics – Open Interviews (MAXQDA12)

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Interviews including which Stakeholders referred each topic, how many of them did and

what solutions and alternatives did they present - can be seen in APPENDIX F.

Figure 10 - Topics 'Solutions' and ' Alternatives'

4.2 Jamming Trial

During the three jamming trials, when the Jamming signal was powerful enough,

due to the proximity to the GPS antenna, several equipment failed. This can be shown and

described on Table 5 and pictures are shown in APPENDIX G.


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EQUIPMENT MESSAGE DESCRIPTION

AIS “No sensor position in use”

Figure 60 (APPENDIX G)

No positioning sensor was

available.

AIS “UTC Sync Invalid”


AIS could not synchronize it’s

time with GPS due to its

unavailability

ECDIS “No Fix”


“UTC AIS: sync invalid”


No positioning sources.

AIS could not synchronize it’s

time with GPS due to its

unavailability

GPS “No Fix”



ARPA Radar “Position: Loss of Position GPS1”



Sailor VHF “Cannot acquire synchronization at

the satellite channel. Please

initiate a scan”


Sailor VHF could not find any GPS

Satellites.

Sailor VHF “Hardware Problems. Distress

button failure. Distress button

may no longer work”


Distress button could not work

without any positioning.

Table 5 - Equipment failure during Jamming Trials

The following figures show, the results that were obtained during the First, Second

and Third Jamming Trials. The Latitude, Longitude and Speed Variation was null in the

periods where the jammers were effective (as there was no positioning or speed data).

The graphs show the variation in meters per minute, for the Latitude and Longitude and,

in knots per minutes, for Speed.

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4.2.1 First Trial

For this particular trial, vertical bars are shown when there was no positioning,

navigation or timing information (when the latitude, longitude or speed variation was

zero), which means that the position at some points was null (Position 2 – Position 1 = 0).

This means that at these points - where the vertical bars were shown and there is no

position or speed variation - the jammers were on.

Figure 11 - Latitude Variation (1st Trial)

Figure 12 - Longitude Variation (1st Trial)


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Figure 13 - Speed Variation (1st Trial)

4.2.2 Second Trial

Similar to the first trial, vertical bars are shown when there was no positioning,

navigation or timing information (when the latitude, longitude or speed variation was

zero), which means that the position at some points was null (Position 2 – Position 1 = 0).

This means that at these points - where the vertical bars were shown and there is no

position or speed variation - the jammers were on. Nevertheless this test was not as

conclusive as the first - due to some values not being as regular as in the first trial as the

naval unit was anchoring in harbour.

Figure 14 - Latitude Variation (2nd Trial)

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Figure 15 - Longitude Variation (2nd Trial)

Figure 16 - Speed Variation (2nd Trial)

4.2.3 Third Trial

Similar to the second trial, this test was not as conclusive as the first due to some

values not being as regular as in the first trial – the naval unit was anchoring in harbour,

leading to some unexplainable values and small positioning and speed variation.


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Figure 17 - Latitude Variation (3rd Trial)

Figure 18 - Longitude Variation (3rd Trial)

Figure 19 - Speed Variation (3rd Trial)

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4.2.4 Spectrum Analyzer

The Spectrum Analyzer, R&S FSH3, was used in order to see the difference

between a “no-jamming” period and the jamming periods, in terms of the frequencies.

This made it possible to see that during the jamming periods the SNR was much higher

than during the no-jamming periods. These intense signals – transmitted by the jammer

– operating in the GPS L1 band, “drowned” the true GPS signals and lead to no PNT

information, during the three trials. This can be seen in Figures 20 and 21, using the J242-

G and J220-B model, at different distances from the ship’s GPS antenna.


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Figure 20 - Spectrum Analyzer (J242-G model)

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Figure 21 - Spectrum Analyzer (J220-B model)


77

Chapter 5 – Analysis

5.1 Portuguese PNT stakeholders

Portuguese Organisations believe, generally, in the need of Availability in PNT

services and, it should be a requirement for a resilient PNT system. There should be a

higher investment in implementing local systems, such as Pseudolites or training

complementary navigational methods, like Celestial Navigation. Most of the organisations

have backup systems in case of GNSS unavailability, but consider themselves GNSS

dependent in order to maintain normal service functioning. The previous results can be

seen on Figure 22 below.

Figure 22 - Questionnaire results

The personal interviews helped comparing the different stakeholder’s groups and

analyse all the similar elements that they share, in a more complex way.

Two concept were highlighted by an Academia Stakeholder during the Personal

Interview: Efficiency and Resilience. He believes that one of the problems the future

generation will be confronted with is the lack of the resources that are used to produce

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components for electronic systems like satellite vehicles. This means, in this stakeholder’s

opinion, countries may choose to adopt a resilient or an efficient strategy, which he

explained in the following way: “if a country has a saving economic strategy with low

investment, in a crisis situation, there will be a saved fund ready to be used. This is

resilience. The result will be slow economic growth but, also, high capacity of recovering

in a hazardous situation. In the efficiency strategy, the aim is to reduce the stock and

increase the investment. This leads to a more dynamic and growing economy,

disregarding the capacity to recover in an unpredictable event.”217

The concept of Redundancy was also dominant, as the Stakeholders believe there

should always be a redundant back-up system. It can be, per example, having two GPS

receivers, having GPS and a Maritime Inertial Navigation System or, simply, using Classic

Methods (ex: Celestial Navigation), that are still being used and do not depend on any

signal reception or advanced technology.

In general, most of the GNSS’ performances parameters were referred like the

importance of Precision, Accuracy, Integrity, Availability, Continuity, Robustness,

Coverage and Reliability for the quality of their products/services or, in some cases,

personal safety (for example during flight procedures). “In open-sea there is not a

necessity, as high as in coastal waters, of accuracy and reliability”218. It was also stated

that constellations should be designed in order to cover as much area as possible and for

satellites to have the longest useful lifetime possible: “When all the satellites (GALILEO)

are in orbit, there will be permanent global coverage”219.

Another topic referred was the importance of costs. “There should be Portuguese

alternatives to GNSS but, are the costs worth it?”220 Most of the stakeholders that referred

this topic believe that, due to the Portuguese socio-economical context, it is not crucial

and favourable to invest in this area. Rather than the initial investment there is, still, the

maintenance component which involves high periodic costs. “What I can see in a near

217Translated by the Author. 218Translated by the Author. 219Translated by the Author. 220Translated by the Author.


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future is significant maintenance cost, as stations will need maintenance and updates.

Who is going to pay for this?”221

Vulnerability was also a topic constantly being repeated. We are vulnerable if we

depend, only, of American (GPS) and Russian (GLONASS) GNSS. Critical and emergency

services do not use GPS as a primary method due to its vulnerability and possible

unavailability (ex: INEM; Stock Exchange, etc.). “Something that really depends on time

synchronism is the Stock Exchange. If it collapses it’s over. A nanosecond can be

enough”222. In a crisis situation, the primary systems tend to fail first and, it is in these

types of situations, that we can see how vulnerable we are. “If everything fails and there

is no knowledge, I cannot work”223.

Another interesting fact is that some stakeholders believe we are vulnerable just

by having to go back to traditional methods if all GNSS fail. “It is always harder to go

back”224. Nevertheless, some specified that it is not trivial that all systems should fail at

the same time and, in some systems, a temporary fail will not have any impact and may,

even, be detected and automatically corrected.

According to the Methodology used for this project for analysing Organisations,

some important elements were: Reconceptualization; Studying what goes right;

cultivating requisite imagination; and acknowledging and managing variability225. For this

mean, several solutions, were presented by the interviewees for a resilient Portuguese

PNT future:

Implement a PNT National Strategy;

Government financing on national PNT projects and working groups;

Government funding and creation of a directive structure to promote PNT

research in Portugal (create a National PNT Council);

221Translated by the Author. 222Translated by the Author.

223Translated by the Author.


225Christopher Nemeth, Erik Hollnagel, pp xiii-xv.

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Create a Jamming and Spoofing Testing Perimeter (like the U.S.’ White Sands

Missile Range) for GNSS researchers, developers and military use;

Population’s awareness of the GNSS’ flaws;

Invest in Multi-constellation;

Portugal adopting GALILEO as a EU PNT strategy;

Promote an open public debate for PNT strategies;

Classic methods training for positioning, navigation and timing (ex: Celestial

Navigation);

Use of more robust DGPS Stations;

Invest in e-LORAN;

Adopt alternative PNT systems;

Adopt national alternatives with coastal and harbour coverage;

Make sure, in the Portuguese Navy, that internal and North Atlantic Treaty

Organization (NATO) navigation doctrine is being put to practice;

Implement Autonomous Navigation System in Warships;

Create an integrated national PNT system with several unclassified systems

for civil and military use;

Use multi-frequency systems (less vulnerable to jamming);

Use independent PNT systems for redundancy;

Create systems with flexible architectures that are able to detect failures or

flaws and quickly mitigate them (Model adaptation, failure and exception

handling as key-aspects of a resilient system, stated in Chapter One).

For these alternatives to be implemented or for the development of a new

integrated national PNT system, there needs to be a resilience monitoring plan to identify

which failures lead to the complete loss of the system and which ones the system is able

to recover from. If the system is available after irregularities occur, it means it is flexible.

All the interviewees, whether they use GNSS for positioning, navigation or timing

means, considered that their dependency is high (some even depend exclusively on it), in

order to achieve their daily work objectives. On the other hand, they all consider that it is


81

possible to keep going on if the GNSS they use are unavailable. It will, simply, take longer

than usual and some concepts must be revised such as: Classic Topography or Celestial

navigation. “We should invest more in Celestial Navigation and practice it more, it is useful

knowledge and should not be forgotten”226.

Some stakeholders confessed that they are not specifically prepared in case of

GNSS failure and that the population is not able to reach an unknown destination without

GPS anymore as it is used for almost everything. Nevertheless, they acknowledge the

vulnerability and do not neglect classic methods training as an, always available,

alternative.

Some systems operated aboard Portuguese Warships depend, exclusively, on GPS

information and have the capability to send out an alarm in case of a GPS unavailability

period. If they are not available, the information superiority that the Portuguese Navy is

supposed to have to compile the actual maritime picture, will be severely compromised.

The National Network for military and civil use (for organisations that require high

precision and accuracy services), SERVIR (provided by the Portuguese Army), is not

available if there is no GPS signal. Also, the national service for maritime pollution

assistance (Serviço de Combate à Poluição no Mar) also uses GNSS in case of maritime

pollution incidents.

Currently, the problem is not solely the GPS dependency: “We are not so

dependent on GPS anymore but we are dependent on GNSS.227”

The Portuguese PNT Stakeholders already have several GNSS (more specifically

GPS) alternatives in use or in development (in partnership with other countries):

Radar Navigation – necessary to always know the constraints that it implies

to the levels below (Constraints)228;



228Nancy Leveson, pp 12-13.

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GALILEO, as a civil GNSS, will be less vulnerable in case of political or military

conflicts - there needs to be communication between the different levels of

control for effectiveness (Levels of control) as described in Chapter 3229;

GALILEO’s Public Regulated Service (similar to the Military GPS service) is less

vulnerable to jamming and spoofing (larger frequency spectrum) - a

relationship between the different variables is required for the actual state

to correspond to the process model (Process models)230;

With the completion of GALILEO’s satellites constellation, there will be total

global coverage and interoperability between GALILEO and other

constellations - improving the signal in urban canyons;

The fact that GALILEO will help Search and Rescue through a connection with

COSPASSARSAT – a relationship between the different variables is required

for the actual state to correspond to the process model (Process models);

GALILEO will have four atomic clocks (greater time reference accuracy);

Multi-constellation (when all GNSS have fully operational capability) is

expected to make it possible to know on which side of the road a destination

is - there needs to be communication between the different levels of control

for effectiveness (Levels of Control);

The use of RTK as an alternative - a relationship between the different

variables is required for the actual state to correspond to the process model

(Process models);

The use and training of traditional methods (Celestial navigation, classic

topography and hydrography) - necessary to always know the constraints

that it implies to the levels below (Constraints);

The use of Visual Landmarks navigation and Dead Reckoning(“Determination

without the aid of celestial navigation of the position of a ship from the

229Nancy Leveson, pp 12-13. 230Ibidem.


83

record of the courses sailed, the distance made, the known starting point

and the known estimated drift”)231 - necessary to always know the

constraints that it implies to the levels below (Constraints);

The use of marine paper navigation charts in order to keep the position

updated - there needs to be communication between the different levels of

control for effectiveness (Levels of Control);

The use of the National Geodetic Control Network - a relationship between

the different variables is required for the actual state to correspond to the

process model (Process models);

The use of Marine Inertial Navigation Systems - there needs to be

communication between the different levels of control for effectiveness

(Levels of Control);

The use of the Doppler Radar Systems - there needs to be communication

between the different levels of control for effectiveness (Levels of Control);

The use of GGPS (Geodetic GPS) for hydrographic means - there needs to be

communication between the different levels of control for effectiveness

(Levels of Control).

5.2 Portuguese PNT actual picture

Based on the Online Questionnaire and the Personal Interviews, an actual Portugal

PNT picture was created and can be seen on Figure 23. The solutions and alternatives that

have not even started developing (some may never be developed as they are personal

opinions of the interviewees) are represented in red. The solutions represented in orange

are in development but still in a precarious state. The alternatives and solutions

represented in yellow are in development but still not close to being fully developed. In

green, are the solutions or alternatives that are already being used or ready to be used.

231Britannica, Dead Reckoning, https://www.britannica.com/technology/dead-reckoning-navigation,

(accessed July 2017).

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Figure 23 - Portuguese Actual PNT Picture

Analysing, both, the Online Questionnaire data and the Personal Interview data, it

can be seen that most PNT Stakeholders believe that something should be done about

Portugal’s dependency on Europe, Russia, United States of America and China for PNT

information. Nevertheless, most also recognize that in the actual financial and social

Portuguese picture, it is not advantageous to invest in regional alternatives or developing

our own PNT systems. Firstly, there is a common perception of low probability of, in the

nearest future, losing both NATO and EU alliances – which means Portugal will be able to

advance in accordance with the EU and NATO allies. Secondly, it is assumed that it is very

unlikely that all systems should fail at the same time and, thirdly, most of the stakeholders

stated that they have alternatives. These alternatives may be robust PNT systems or

simple classic methods for obtaining PNT information.

By analysing the Personal Interviews, it was possible to conclude that the concepts

that emerged from the interviews all relate to each other, according to Leveson’s advices

presented in Chapter 3 – Definition of the task; data collection; construction of the


85

hierarchical control structure; bad control analysis; and review and analysis of

accidents232:

GNSS dependency leads to Vulnerability;

In order to mitigate this vulnerability there are alternative PNT methods that

can be used and overall future solutions that can be adopted;

These solutions also include improving GNSS characteristics in order to have

more robust systems;

They solutions are also important for having system redundancy;

Alternative solutions and redundancies have inherent costs;

When considering the costs, there are two possible ways to look at this issue:

through a resilient economic way or an efficient economic way.

5.3 Jamming Trial

The three jamming trials performed in this study were performed over a period of

72 hours, aboard a Portuguese warship. Two hand-held jammers were used: J242-G and

J220-B, already been used during the SENTINEL Project. The J242-G, according to the

manufacturer, has an output power of 2.0W and a shielding radius of 15 metres. The J220-

B model has an output power of 0.4W and a shielding radius of 8 metres. Other

specifications are presented in APPENDIX H. There are not any further detailed technical

specifications due to the language barrier between the Author and the Seller, which failed

to give out further details on the jammers.

To assess the jammers impact on the GPS normal functioning, National Marine

Electronics Association (NMEA) data (Standard data format supported by all GPS

manufacturers233) was directly transferred to a portable computer using a free open

source program named Putty234 with a R232 cable, during normal operations and jamming

232Nancy Leveson, pp 25-30. 233Erik Gakstatter, What Exactly Is GPS NMEA Data?, GPS WORLD, 2015, http://gpsworld.com/what-exactly-

is-gps-nmea-data/, (accessed June 2017).

234http://www.putty.org/

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periods. After parsing the NMEA data, it was computed in order to find out the variation

between each latitude and longitude coordinates and, also, speed values, leading to the

graphs previously presented in Chapter 4. In the raw data, before it was computed, during

the jamming periods the positioning data – latitude and longitude – was null which means,

after it was processed it was possible to see – graphically - the effective jamming periods.

The data extraction was made directly to the computer through the open source

FSH View Software235. This led to surprising facts as the jammer that was thought to be

more powerful, the J242-G model with a total output power of 2.0W, turned out to be the

least effective. The J220-B model was the most effective (and cheapest) model used.

When turned on, instantly all the GPS dependent systems tended to fail – with a radius of

30 metres. The normal GPS signal is very weak by itself, due to the satellite-receiver

distance, so these values were only possible because of the jammers. This can be proved

comparing the “no-jamming” periods with the jamming periods screenshots, previously

presented in Chapter 4.

Figure 24 - R&S FSH3 Spectrum Analyzer

In all the three trials, different distances to the GPS antenna were used for each

jammer: 1m, 10m, 30m and 50m approximately.

When the J220-B model was operating, alarms sounded on the bridge making the

environment more hostile and stressful. Nevertheless, the surprise factor is very

235https://www.rohde-schwarz.com/software/fsh/


87

important and, in this case, it was not possible to test the crew’s readiness when

submitted to a GPS-denied environment, as they knew that these specific tests were being

conducted. The environment, though, was still stressful leading crew members to

interrogate when the tests would be over. No emergency/solving procedures were found

or used and no technical services were informed. These results and alarms going off were

already partially expected according to GLA’s previous Jamming Trials.

Firstly, most warships operate basic GPS systems, using the C/A-code. These are

vulnerable to jamming when this is not any other physical equipment that can

complement this GPS information loss – which was the case. Secondly, navigation doctrine

that is still being taught and used, is being put to side due to the users trust on GPS for

PNT information. Users know, for a fact, that GPS might not be available but it seems to

be available every day, leading to overreliance and a disregard of more detailed and

complex procedures. Thirdly, there are not any implemented routines of checking if the

GPS and GPS-dependent systems are in normal functionality. Users presume that the

position is correct if there is not any alarm. The fact is, that during the GPS trials, if the

jamming signal was not powerful enough (when there was a greater distance from the

jammer to the GPS antenna), the Radar, ECDIS and GPS did not black out, they simply kept

showing an out of date position that the users do not know if it is trustworthy or not, but

still keep using it as positioning reference.

At last, in case of a jamming event, no internal Standard Operational Procedures

(SOP) was found aboard and there are not any anti-jamming antennas or filters to mitigate

these kinds of events.

On the jamming trials results, the first and third trials were not as reliable as the

first trial due to the fact that the naval unit was anchoring in harbour.

On Table 6, the impact of both jammers can be seen according to the measured

distances (Green – Systems working normally; Yellow – Positioning errors but no alarms;

Red – Alarms and no PNT information).

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Distance(m) MODEL J242-G

MODEL J220-B

1

10

30

50

Table 6 - Jammers impact (1,10,30,50m)

On Figure 25, a vulnerability assessment is made due to the crew’s behavior and

implemented routines.

Figure 25 - Vulnerability assessment

Observing Figure 25, one may easily conclude that if there are not implemented

routines for checking the GPS and GPS information dependent systems; if an alarm goes

off and the technical services are not aware; or if there are not any internal procedures

implemented for this specific case: a Warship is possibly vulnerable when submitted to a

GPS-denied environment.


89

The main question of the Project, “Why should PNT Systems be resilient?” was

responded throughout the Project Report. PNT Systems should be resilient in order to

predict, avoid and mitigate possible accidents. HRO, like the Portuguese Navy, depend on

continuous PNT information for maintaining information superiority and to be able to

operate in calamitous scenarios. This means that the PNT systems they operate, per

example, in Warships, should:

Send out warnings when in a degraded condition;

Have flexible architectures;

Be able to quickly recover when submitted to hazardous conditions;

Have redundancies;

Operators should have routines for a proper system’s-health assessment

and procedures in case there is equipment failure.

This is only possible if there other PNT alternatives do not exist aboard, apart from

the GPS, whose vulnerabilities have been referred throughout the report.

According to the secondary questions: “How can a PNT System be resilient?”

Briefly, a PNT System is resilient if:

It serves all types of navigation (Restricted Waters Navigation, Coastal

Navigation and Open Sea Navigation);

It is compatible with augmentation systems;

Allows unlimited users;

Operates with geodetic and time reference systems;

It informs the users if degradation occurs;

It is compatible with shipborne equipment;

It is accurate; precise; available; reliable; continuous; has integrity

monitoring and know its integrity risk.

“What are the Portuguese PNT Stakeholders looking for in a PNT System?” The

Portuguese PNT Stakeholders are mainly looking at the following performance

requirements in the following order:

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Availability;

Continuity;

Precision;

Accuracy;

Coverage;

Integrity.

Also, they believe that the best possible alternatives to GNSS would be the

creation of Local Systems – Pseudolites was presented as an example for these systems in

the questionnaire - and Traditional Navigation Training (ex: Celestial Navigation). Most of

them depend on PNT systems for Positioning, Navigation and Timing in the previous order.

“What is the current perspective of PNT Systems in Portugal?” Currently Portugal:

Is taking part, with the EU, in the GALILEO Project;

Has Differential GPS in use and operational;

Has Doppler Radar Systems in Aircrafts;

Has a National Geodetic Network in currently available;

Radar Navigation and Visual Landmarks are possible independent to PNT

alternatives;

Real-Time Kinematics are currently being used;

Classic Navigation Methods are still being taught in Military Academies and

Universities.

However, Stakeholders believe that we should invest in e-LORAN; have a

Government fund for PNT; finance PNT working groups; create alternatives for harbour

and coastal coverage; implement multi-frequency systems and create a National Test

Perimeter for assessing system vulnerability.

“Are the Portuguese Warships vulnerable to (un)intentional GPS information

denial?” Most Portuguese Warships’ GPS systems operate the SPS with the normal C/A-

code. Only few of them operate the P(Y)-Code. This means, they are not immune to


91

(un)intentional jamming and, only few, are partially protected from Spoofing through the

P(Y)-code. Apart from this:

There are no internal procedures for assessing the GPS System’s health

periodically;

There aren’t any anti-jamming antennas or filters;

There aren’t also procedures in case there is GPS unavailability;

There are no training programs for this matter in the Portuguese Navy’s

internal training plan.

It is highly recommended, in a near future, to integrate other PNT Systems with

our traditional outdated GPS System, like Inertial Navigation Systems, and make a national

assessment on how anti-jamming antennas should be implemented and how they should

be positioned.

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Chapter 6 – A path for a resilient PNT System in Portugal

Firstly, in order to create a national resilient PNT system, it is important to think

back on what characteristics make a system resilient. As referred before, a resilient system

should have the capacity to:

Handle its own failures;

Manage exceptional events;

Adapt according to the business and organisational environment;

Handle changes that were not predicted when the models were designed;

React in case “cascading” events occur236;

Have the capacity to absorb disruptions without having a breakdown;

Be flexible and respond to external changes;

Have a considerable margin to the performance boundaries;

Be tolerant and have healthy interactions between the scales above and

below.237

Most of the Stakeholders interviewed in this project have back-up systems in case

the PNT systems they use, fail. Nevertheless, one the factors that, most of them,

considered vital for responding to their daily service needs was Availability. This is not,

always, possible when the only PNT System they operate is a GNSS, due to several

intentional or unintentional factors that have been referred before. Throughout this

project, also, the vulnerability of a Portuguese Warship was tested, when submitted to

GPS-denied environment and, the results, were not positive. There were not any

redundant systems, pre-planned responses or routines for responding to these matters.

According to the theoretical approach initially made, the Questionnaire and

Interview results and the GPS Jamming Trials, the following advices can be considered

individual steps for creating a path to a Portuguese Resilient PNT System:

236Pedro Antunes, Hernâni Mourão, pp 7-9.

237Erik Hollnagel, David Woods, Nancy Leveson, p 23.

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1. Population and Government Awareness – explain GNSS’ possible

vulnerabilities and show other countries’ progress on PNT alternatives;

2. Promote a Public Debate – PNT Stakeholders should discuss Portugal’s PNT

future and possible solutions;

3. Create a National Budget on PNT;

4. Designate a National PNT Authority – the Portuguese Government should

designate a new PNT Cabinet for projects approval and coordination;

5. Promote PNT investigation groups – for investigating and developing resilient

alternatives;

6. Create a National Test Perimeter – to submit projects to adverse conditions;

7. Invest in National Industry - or lead agreements with international industries

for manufacturing;

8. System Tests – is it independent? Does it work in critical situations? Does it

have a flexible architecture? Does it recover from unpredicted events?

9. Implementation Plan – according to Portugal’s economic situation, the

stakeholders should be the ones to invest in new equipment for operating

with a new PNT System (it is not utopic if they are shown the advantages of

moving forward);

10. Keep participating and bringing new alternatives to international projects to

create funds for project support;

11. Integrate our new resilient PNT System with other systems - for redundancy,

global coverage, permanent availability, greater precision and accuracy and

reliability;

12. Periodic collection and analysis of Stakeholder’s feedback;

13. Periodic National Conferences - for development and upgrades;

A visual representation of these measures can be seen on APPENDIX J.

This process is expected to a take long time until it is fully implemented as it

requires funds, complex engineering and an urge to develop and enrich the Portuguese

participation in the PNT Industry.


95

However, there are several actions that can be implemented in a short period of

time, especially in the Portuguese Navy (which was studied in greater detail during this

project) such as:

Implementing existing doctrine for Piloting and Navigating in Coastal waters;

Creating SOPs for responding in a hazardous environment (per example,

when submitted to Jamming or Spoofing);

Include these procedures in the National Basic Training Plan for Warships;

Create internal technical procedures for improving the resilience of the

equipment receiving the GNSS signals (according to the U.S. Department of

Homeland Security’ report238). No internal procedures were found for this

matter, during the research made in this project.

238United States Department of Homeland Security, pp 5-6.

96


97

Conclusion

In the development of this project, the concepts that were necessary for

understanding the definition of Resilience and PNT Systems were studied. Using this

theoretical approach, doing questionnaires, personal interviews and a Jamming Trial,

made it possible to conclude what is the actual Portuguese PNT Picture; which is the path

for developing our own resilient PNT System; and to understand how vulnerable the

Portuguese Warships when submitted to a jamming attempt.

High Reliability Organisations need to have their main services guaranteed in

critical situations. This means they must operate resilient systems for being able to

assume control and have information superiority in catastrophic scenarios. The

Portuguese Navy is one of these HRO that is several times submitted to operate in

hazardous conditions, where positioning, navigation and timing data is crucial for mission

accomplishment. However, if the actual PNT Systems aboard the Portuguese Navy

Warships are not upgraded, they will always be vulnerable to intentional GPS-denial

events, like jamming or spoofing. The same situation applies to all the Organisations and

National Services that depend, only or mainly, on GPS.

The methodology for analysing the Questionnaires and Interviews was quite

complex as some parameters could not be compared. The organisations or individuals

that were interviewed, belonging to a Stakeholder group, were not totally representative

of that group, making the data unable to be totally conclusive. In order to perform a valid

analysis, more representative elements of each stakeholder group should have been

interviewed, which would require a greater time period for this part of the study.

The methodology used for assessing the Portuguese Navy’s vulnerability helped

realizing that prevailing internal and NATO doctrine should be enforced and, procedures

and pre-planned responses for vulnerable conditions, should be implemented and

trained.

98

The methodology used for the Questionnaires and Interviews to the Stakeholders

helped to realize how vulnerable Stakeholders consider themselves by operating GNSS

and if they have systems or procedures as alternatives or back-ups, in case of GNSS

unavailability. Moreover, it was possible to create the actual Portuguese PNT picture

based on the Stakeholders opinions and create a path to develop a resilient Portuguese

PNT System.

Overall, the initial objectives were accomplished. Nevertheless, some

particularities could be improved such as the possibility of performing more Jamming

Trials in different Naval Units in order to assess if the conclusions would be similar; have

a more equal representation of each group of stakeholders for better data analysis; and

do further analysis on the Spectrum Analyzer data for more detailed and technical

conclusions.

There were several constraints during the project, especially the theoretical

approach that had to be performed before and after the jamming trials. Before the

jamming trial it was necessary to define procedures and understand which systems

depended on GPS information, to enable the data extraction. After the Jamming Trial, the

same process had to be repeated for executing the NMEA data analysis. Also, getting in

touch with the Stakeholders was not trivial. Firstly, because of the short period of time

available for this matter and, secondly, because some organisations and individuals never

replied to the questionnaire and interview request.

As a final suggestion for future projects: It is recommended to perform a study on the

GPS antenna installation aboard Portuguese Navy Warships and the creation of internal

doctrine for this matter, with the intent to reduce vulnerability, make the receivers more

resilient – per example installing Radiofrequency filters or CRPA – and implement new

resilient PNT alternatives.


99

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APPENDIX A

Description: The informative leaflet that was e-mailed do every Portuguese PNT

Stakeholder.

Figure 26 - Stakeholder's request for participation

108


109

APPENDIX B

Description: The Online Questionnaire, through Google Forms, that was answered

by all the interested PNT Stakeholders.

Figure 27 - Questionnaire (page 1)

110



111


112



113

APPENDIX C

Description: This Appendix shows the graphs (made through Microsoft Excel) that

were made according to the Online Questionnaire data.

Figure 31 - Open interview analysis (Users - Time)

114

Figure 32 - Open interview analysis (Academia)


115

Figure 33 - Open interview analysis (Investigation)

116

Figure 34 - Open interview analysis (Users - Navigation)


117

Figure 35 - Open interview analysis (Users - Positioning)

118

Figure 36 - Open interview analysis (Control & Vigilance Authorities)


119

Figure 37 - Open interview analysis (GNSS-depend services supplier)

120

Figure 38 - Open interview analysis (GNSS services supplier)


121

APPENDIX D

Description: This Appendix shows the Personal Interview that was answered by all

the interested PNT Stakeholders.

Figure 39 - Personal interview

122


123

APPENDIX E

Description: This Appendix presents a Mind Map for the results of the Personal

Interviews, according to the topics that emerged from the interviews analysis, after

several iterations of the coding process.

Figure 40 - Common topics (1)

124




125



126




127


128


129

APPENDIX F

Description: This Appendix shows a Mind Map based on the results of the Personal

Interviews (which Stakeholders referred each topic and how many of them did).

Figure 48 - Personal interview results (1)

130




131


132




133



134


135

APPENDIX G

Description: This Appendix shows pictures of the Jamming Trials aboard a

Portuguese Navy Warship.

Figure 56 - R&S FSH3 Antenna

Figure 57 - Trial equipment (R&S FSH3)

136

Figure 58 - Putty program

Figure 59 - R&S FSH3


137

Figure 61 - AIS "UTC sync invalid"

Figure 60 - AIS "no sensor position"

138

Figure 62 - ECDIS (AIS alarm)

Figure 63 - ECDIS (No fix)


139

Figure 64 - Radar KH1007 (loss of position)

Figure 65 - GPS Furuno - no fix

140

Figure 66 - VHF sailor (no satellite sync)

Figure 67 - VHF sailor (distress failure)


141

APPENDIX H

Description: This Appendix shows the Technical description of both Jammers used

(J242-G and J220-B).

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143

APPENDIX I

Description: This Appendix shows the illustrative representation of the path for a

resilient PNT system in Portugal.

Documents

Resilience of the PNT Systems - CORE